A Driving Instructor's Blog

Computers & Tech

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Fogged up windowsThis is an old article from 2013, but it is due an update. When I originally published it, one of the show-me-tell-me questions was:

Show me how you would set the demister controls to clear all the windows effectively. This should include both the front and rear screens.

At the time of updating, the relevant show & tell questions (they changed the name) are:

When it’s safe to do so, can you show me how you’d set the rear demister?

When it’s safe to do so, can you show me how you’d demist the front windscreen?

For the windscreen – that’s the one on the front of the car – the universally correct answer would be that you’d switch the airflow to blow out of the vents on the rear of the dashboard up at the windscreen, turn up the fan speed, and increase the temperature of the air from these vents. That would work for any car, although the actual knobs to twist and buttons to press will vary from model to model.

For the rear window, you’d turn on the electric heater that warms those little metal wires stuck to, or embedded in, the glass. There will be a button somewhere on the dashboard that turns it on and off.

You will note that the original broad question has now been changed to two rather more specific ones. This is relevant, because most newer cars also have air conditioning, electrically heated front windows, and often a button labelled as “MAX”, which turns everything on to demist all the windows very quickly at the same time. One press and you turn on the front and rear window electric heaters, the air conditioning, and redirect the hottest air possible at the windscreen (and often the side windows, as well, if your car has that feature).

When asked the original show-me-tell-me question, operating the MAX button was a perfectly correct response – as were playing around with the air flow controls, using the heated front windscreen if you had one, and turning on the rear window heater. However, with the much more specific Tell questions currently used, pushing the MAX button isn’t strictly the right response to either of them. It is also worth noting that whereas the original question would have been asked whilst stationary, if either of these new ones are asked, it will be while the candidate is driving. Ever since they started doing it this way, I’ve had nightmares about people fiddling with buttons and dials while taking a bend and losing control (I know the examiner would prevent that, but at the very least it would result in a test fail).

Arguably, operating the MAX button is a satisfactory response to either question, because it will achieve the desired result. But it is technically not the correct response if you’re being pedantic about it, because it does several other things at the same time.

It makes sense to understand all the controls rather than just blindly push buttons and twist knobs. If nothing else, if you inadvertently turn the car into a sauna, you ought to know how to turn the temperature back down again – and you’d be surprised by how many people can’t work out for themselves that if you turn something on by pressing a button or flicking a switch, you can usually turn it off by pressing the button again, or flicking the switch the other way. It also means that if you respond to the examiner’s question by pressing the MAX button, you’ll probably be able to recover if he specifically asks you to demist either the front or back – but not both.

How does the air-blower demist windows?

It involves a bit of science, but it is enough to know that hot air will demist windows, whereas cooler air probably won’t.

The reason it works is down to relative humidity. Air can hold water vapour as a gas, but if the amount of vapour reaches the maximum that the air can hold, it precipitates out – condenses – as water droplets. That’s the “mist” on the glass. The problem is that the maximum amount of vapour the air can hold before condensation occurs gets less and less the colder the air is. If you refer to water vapour in air as the “humidity”, then the amount of vapor relative to the maximum possible is the “relative humidity”. In summer, a relative humidity (RH) of 70% might feel horribly sticky and sweaty – but there’d be no condensation. In winter, you can easily get 100% without feeling it because there’s a lot less moisture there– but since there’s no room for any more vapour in the air, any extra causes condensation to take place. Think of it as a bucket overflowing, where the colder it is, the smaller the bucket is.

What happens is that on cold mornings, with the air at – or very closer to – 100% RH, as soon as you get in the car, breathing and perspiring, you overflow the bucket and condensation takes place. You see it on the glass as mist, but everywhere feels slightly damp. When you initially turn on the heater, it is blowing cold air, and if anything you get even more misting. But as the car warms up, it starts to blow warmer air. This warm air can hold more water vapour, and it evaporates the mist as it blows across it and keeps hold of it.

What does the air conditioning do?

Air conditioning (A/C) units pass the air over a radiator filled with coolant – just like what you have in your fridge at home. If you look back at what I said about humidity, above, you can probably work out that if you cool very moist air, you send it above 100% RH. The excess moisture – and if you cool humid air at 30°C down to 8°C, there’ll be a lot of it – condenses out (usually as a pool of water under your car in summer if you’re stopped), and much cooler and drier air is blown into the car. You can play around with the temperature of the air that is blown in by passing it over the heater radiator, so you have crude climate control.

Since it removes moisture, A/C is extremely efficient at demisting and preventing further misting.

How do the heated windows work?

In a similar way to the air blower. As they heat up they create an area around the metal wires which is warmer and so the mist evaporates back into the air. They work best in conjunction with the car heater, which heats the bulk of the air in the car, and which can then keep hold of the vapour, preventing condensation. They work even better with the A/C, because it strips the vapour out and dumps it outside the car. The MAX switch activates everything in one go.

How do you control these features?

It varies from car to car, but for the heater blower, there will be several rotary controls usually located in the centre of the dashboard and below the level of the steering wheel.

Heater controls

One of them controls the speed (and noise) of the fan, one controls the temperature (blue is cool, red is warmer), and another allows you to select which vents and grilles the air will be blown through (at your feet, at your face, at both, or at the windscreen – possibly with other combinations).

Higher spec cars may have digital temperature displays, and some will have independent control for each side of the car. Some will even have controls in the rear for back seat passengers.

Heated Front Window Symbol

Heated Rear Window SymbolThe heated rear window button will have an icon like the one on the left, and the heated front windscreen will have one like that shown to the right.

The air conditioning will be activated with a button or switch marked A/C, and the MAX button (which activates all of these features) may also have one of the window icons.

Isn’t the heated windscreen for de-icing?

Not specifically, no. It serves the exact same purpose as the heated rear window – to demist. However, every demisting feature in the car can also de-ice if necessary. Even blowing cold air can lead to de-icing if it isn’t too cold, because the air passing through even a cold car is still warmer than that outside. However, a heated front window is noticeably useful at de-icing since that’s the very window that needs de-icing the most.

Having said that, a heated windscreen is only good at melting frost or dislodging a thin layer of rimed ice. If you think it’s going to get rid of a couple of inches of snow, think again. It doesn’t actually get that hot – if it did, it could cause the glass to shatter.

Why do my windows steam up in summer if it’s been raining?

That’s because water cools as it evaporates. If it’s already humid when it rains, the air passing over the windscreen evaporates the rain drops, so you get cooling around them. The humid air inside the car is then above 100% RH close to these spots on the windscreen, and condensation occurs. You usually see it around spots of rain.

You can also get it if you’ve had the A/C on. It cools the windscreen right down, so when you turn the A/C off and humid air gets back in, the cold zone near the glass sends the RH there above 100% and condensation occurs. In this case, misting is more uniform, but often concentrated on the lower part of the windscreen where the A/C has been blowing.

So what should I tell the examiner on my test?

Your best bet is to answer the question he’s asking you. If he asks how you demist the back window, operate the heated rear window switch or button. If he asks how to demist the front, either demonstrate how to redirect the air flow and increase the temperature and fan speed, or operate the heated windscreen button or switch (if your car has it).

In Nottingham, examiners have not been querying use of the MAX button, so use it by all means – but just make sure you know how to activate just one of the features as necessary if your examiner presses you on the subject. You are being tested on “safe driving for life”, so you ought to know what the buttons do anyway – you’re going to need to if you pass.

Since these questions are asked while you’re driving (and since you’ll be driving when you use them once you pass), be careful not to stare down and lose control of the car.


Ford Focus One-Touch Window ButtonsMy Focus has one-touch electric windows. On my last car, shortly before it was due for a service, the driver-side window developed a fault whereby when it was closed and hit the top of the frame, it bounced half way back down. What I had to do was carefully inch it up and make sure it didn’t hit the top each night when I got home and locked it up. There was still a small gap, though, but it had a service booked and we had no rain, so it wasn’t an issue.

The dealer fixed it and simply said it had been “reset”. I had no further problems with it.

I have another car now, and it has started doing the same thing. It isn’t anywhere near ready for a service yet, so in order to avoid the inevitable assessment visit and probable brake bleed my dealer would insist on before fixing it under warranty, I looked into it a little further. And big surprise, it is quite common on Fords (and other makes, apparently).

From what I can gather, the reset procedure is to put the window all the way up holding the button, and then keep it held for 3 seconds. Then, push the button and put the window all the way down, then keep it held for another 3 seconds.

But that doesn’t work by itself, because as soon as the window hits the top of the frame, down it comes again. It seems to be connected with the safety feature that prevents idiot kids (and dogs) getting their heads squashed if the window goes up while they’re leaning out. A sensor detects the resistance and winds the window back down again.

The trick is to use a piece of paper or thin card when you do the reset. Hold it just under the top window frame recess and put the window up. Hold the button for 3 seconds. The paper acts as a cushion and prevents the sensor triggering. Now put the window down and hold the button for 3 seconds. That should now have reset the sensor and the window goes up and stays up.

It ought to go without saying – but I’d better say it anyway – do not use anything hard as your cushion, otherwise you’re likely to break the glass. Use paper, and fold it once or twice as necessary to get enough cushioning to stop the auto-retraction kicking in while you do the reset. And keep your bloody fingers out of the way when you’re doing it. Don’t say I didn’t warn you!

My windows bounce back when they reach the top

You may have a faulty motor or sensor, but from my experience it is most likely just needs a reset. Follow the instructions above. That should reset it.

My windows come down on their own

I have read that on some models there is a feature which automatically opens the windows when it gets hot – even when it is unattended, and sometimes in the middle of the night. I have also read that the windows in some cars can be controlled from the key fob, and this can get pressed whilst in someone’s pocket. The sources for this are various web forums, and are not really to be trusted, but even if such a feature existed, I can’t believe that would be available in the UK because the car would get stolen almost immediately in some areas.

It is possible you need to do the sensor reset without knowing it, and the windows actually opened before you locked it up but you didn’t notice. That’s just a thought, and I’m not saying it’s right. But the first time I experienced the bounce back I didn’t realise until I went out again and saw the window open.

If I woke up to open windows, I’d book it into my dealer pronto.


Li-ion generic batteryI’ve had a Nextbase 612GW for over a year now. It records in 4k – meaning that you can see number plates and other details much further away and much more clearly than on other dashcams.

I’m actually on my second unit. Within a year, my first one stopped turning on automatically, and after discussions with Nextbase, they gave me an authorisation code so that Amazon would accept the return and refund me. I bought another in lieu of the refund.

What had happened was that the internal battery had died. It would barely run for 30 seconds after a four hour recharge, and since it is the battery that provides the camera with enough residual power to detect when the power systems in the car are activated (which tells it to turn on and start recording), it was kaput. It worked perfectly if I powered it on manually each morning once a bit of charge had gone to the battery, but any power down lasting more than an hour and the battery would drain again.

Any 4k video device right now gets warm when it is in use, and the 612GW is no exception. I wouldn’t say it gets hot, but certainly very warm, and with the summer we had in 2018, it got warmer still. Li-ion and Li-Po batteries are degraded by high temperatures, and I suspect that overall this contributed to the battery going as quickly as it did. OK, it may also have been a bad batch (or just a bad one in my case), but I didn’t go into that with Nextbase. I’d had it replaced, after all.

It is worth noting that Nextbase told me replacing the battery is quite easy, and they supply them if you ask. It does involve a bit of soldering, but I will bear it in mind for the future.

As I understand it, some cheaper dashcams use a capacitor to hold residual power. However, where a battery is involved, this problem of degradation could occur with any model of camera. Indeed, any battery-based dashcam will effectively “break” sooner or later once the battery dies. Exactly the same thing happens with laptops, phones, and tablets – and it is amazing how many people don’t realise it’s just a dud battery which, in many cases, could easily be replaced. It even used to happen with desktop computers, when the coin battery which held the BIOS settings that enabled the PC to boot died (I’ve replaced a fair few of those in the past for people who thought their PC was broken).

I suspect that a lot of the complaints you see about dashcams dying could be a result of this – along with using the wrong types of SD card.


Dilbert scam cartoonThere was a news item on the BBC earlier, which is covered by this article on the BBC website. It tells of an elderly chap, Doug Varey, who saw a pop-up on his computer offering security protection for 12 years at a cost of £556.

A couple of weeks ago, I got an email from TV Licensing (dated 11 October), informing me that my TV licence payment hadn’t gone through, and that I needed to pay before 13 October, otherwise they’d set the debt collectors on me. Within two seconds I had mouthed “f**k off” and clicked the spam button. Then there’s the Virgin Media emails saying much the same thing. And the Sky ones. And don’t even get me started on the avalanche of emails I get telling me I’ve won an Amazon/Iceland/M&S/Sainsburys/Tesco/Argos/etc. gift voucher. Or the latest one where I’ve apparently won a Kia. I’ve had spoofed bank ones before. Even the pop-up ones like that which snared Doug Varey have cropped up from time to time.

The scammers will get nothing out of me. Unfortunately, they rely on people like Doug Varey – and the “thousands” of others who fall for it.

I use Bitdefender Total Security. It alerts me if I go to an infected website, automatically scans anything I download, and prevents any installed software from accessing protected folders unless I tell it otherwise. It also has ransomware protection and spam filtering among a host of other stuff. It doesn’t slow my computer down. And it costs £20 new on Amazon. It is updated frequently with the latest virus definitions.

Over 12 years, Bitdefender would cost me £240. And yet Doug Varey is quoted in that BBC story:

I thought per year, that’s [£556 is £46 a year] quite cheap. And I agreed to sign up for it.

It isn’t cheap in any shape or form. Even more so when you consider that once he’d paid, they then appear to have accessed his computer and forced him to cough up another £4,000 to remove an alleged hacker.

I have a coffee cup with the Dilbert cartoon above on it. Never was anything so true.


NextBase dashcamA bit of advice to anyone using a dashcam. I see a lot of people complaining that theirs is playing up, and other advice to regularly reformat the card – which seems to get a lot of people recording again. I strongly believe that part of the problem is with the card, and not the dashcam. Specifically, people are using the wrong cards.

I have always used SanDisk Extreme cards in my dashcams, and I have not had any problems. Extreme cards are not the cheapest, either. They’re pretty high spec. However, I recently wrote to SanDisk and asked them if Extreme cards were OK to use in such applications. Here is what they replied:

Thank you for contacting SanDisk® Global Customer Care. Please allow me to inform you that for Dashcams & security surveillance cameras, we recommend to use SanDisk® High Endurance Memory Cards since these cards are specially developed for high endurance applications and continuous read & write cycles. These cards are built for and tested in harsh conditions and are temperature-proof, shock-proof and waterproof.

Also, please be informed that using Extreme or Ultra line memory cards on these devices void their warranty.

At this point, it is worth noting that “high endurance” cards are special cards. They’re not easy to get hold of except through specialist suppliers, and your local Currys is unlikely to have them in stock. They cost more than normal cards.

But the upshot is that using Extreme (i.e. high-end “normal”) cards puts them under stress that they’re not designed for. It voids their warranty, but – more importantly if you read between the lines – there is a good chance they will malfunction or play up. I don’t know much about cards from other manufacturers, but I would lay odds that most people with dashcams are using the cheapest card they can find, and that means they’re not “high endurance” types. Most of the time I see people asking what dashcam to choose they always want a cheap one, and the one they end up buying often costs them less than I pay for a SanDisk Extreme card – so there’s no way they’re going to buy a card even close to that.

My current dashcam is the NextBase 612GW. It records in 4k, and on cards up to 128GB (so I get about six hours of footage in a run).  I have never had any problems with Extreme cards, but after the SanDisk advice I invested in a Samsung 128GB high-endurance card.

NextBase doesn’t seem to want to enter into discussion over this and insist that all their devices work with Extreme cards. Their own branded cards appear to be rebranded SanDisk ones. I don’t disagree that Extreme cards have worked well for me, and probably for everyone else when they’re new. But the niggling problems people keep reporting might not be doing NextBase any favours, because I firmly believe that a lot of the reported “faults” are down to those cards protesting at being used outside of their specification, with the user blaming the dashcam.

SanDisk high endurance cards only go up to 64GB at the moment (SanDisk said they’d feed back to their technical people on that), though other manufacturers (e.g. Samsung) produce higher capacity units.


The Chillmax AirEarly in July, I saw this thing advertised on TV. Then, the same evening, I was shopping in Asda and saw it on display. I am an idiot for things like this, and bought it on impulse so I could test whether it worked or not.

As a chemist, I know full well that if you want to cool a large space down effectively you’re going to need something that uses a special refrigerant. From a practical perspective – where people are going to be in that space, and you need to cool for long periods – that’s going to mean some sort of motor-driven compressor, a closed radiator filled with the refrigerant, a big fan to suck air in and blow it across the radiator, and a wide exhaust pipe through the wall or window to get rid of the “removed heat”. Oh, and probably some sort of collection bucket for the condensed water it takes out, because proper air conditioners dehumidify the air they cool.

The Chillmax Air is much simpler. Anyone who has used a normal fan will know that you only feel “cooler” if you’re sweating. That’s because the fan evaporates your sweat, and that evaporation is accompanied by a small cooling effect – it’s called “evaporative cooling”. Conversely, if the surrounding air is very humid, then no matter how powerful your fan is, you will feel little or no cooling because sweat can only evaporate if the air has capacity to hold additional moisture (I’ll explain that a bit more later).  This same evaporative cooling effect can even be used to freeze water – albeit in very small amounts (and if you’re lucky) – when you force diethyl ether (the stuff they used to use as an anaesthetic) to evaporate quickly. The evaporative cooling effect of different liquids varies greatly, and ether will cool down to a very low temperature if you do it properly. However, ether is both highly flammable and toxic, so apart from demonstrating it in the school lab (where I remember it from, along with the massive headache it gave me), it doesn’t have much practical application these days (though early refrigerators used it, which was spectacularly dangerous).

The Chillmax Air uses the evaporative cooling effect of water. The unit consists of a reservoir at the top, which you fill with normal tap water, and this drips down on to a radiator unit which has ten sideways-stacked fibre panels in it through which a fan blows air. The water evaporates from the fibre panels, and the evaporatively cooled air comes out through the front grille. According to the marketing spiel on the TV ad, you’d be forgiven for thinking you’re going to get frostbite if you sit too close. I knew this wasn’t going to happen – but I wanted to know just how effective the Chillmax Air was.

When I set it up and turned it on, the first thing I noticed was that the fan is quite powerful, so you get a good flow of air directed at you – but note that that it’s only about 5″ in diameter, so it can’t beat a proper desk fan for air flow. The next thing I noticed was that the air did seem a little cooler compared with what my desk fan was blowing at me. It also felt different in another way, which I’ll also come to later. But the big question was how much cooler was the exhaust air?

I fired up my trusty data logger and left it in front of my desk fan for 30 minutes for the control data. Then I moved it and suspended it in front of the Chillmax for the same period of time. This is what it recorded (red line is the switch over point).Chillmax Air - temperature recording

The ambient temperature where I ran the test was about 26ºC (it rose by about half a degree because I had entered the room, turned on the TV and my PC, and so on). The Chillmax brought this down by about 2.5ºC (the blip at the end is where it had just run out of water and was starting to warm up again, and I estimate that it might have dropped another degree at most).

So, the Chillmax definitely cools the air that passes through it, albeit by a small amount. Let’s work on the assumption that it would be able to get the same 2.5-3.5ºC drop no matter what the ambient temperature was. It’s for you to decide if that’s worth the investment, but be aware that if the ambient temperature is 38ºC, pulling it down to 35ºC still means it’s damned hot.

But there’s a little more to it than that. I mentioned that the exhaust from the Chillmax felt different to what my fan was throwing at me, and not just cooler. If I was going to try and put a word to it, I’d say it felt softer. I already knew what it was, but my data logger shows it in numbers.

This is the data for relative humidity recorded at the same time as the temperature measurement, above (red line is the switch over).Chillmax Air - relative humidity recording

As I’ve already explained, the Chillmax works by evaporating water on fibrous panels by forcing air across them. So where does the water go once it has evaporated? Quite simply, it comes out as a vapour in the cooled air. Well, most of it does. Some of it actually condensed on to my data logger and began to drip during my test. I have since discovered that it also condenses on the front grille and can drip periodically, so you need to be careful if you put it on a shelf with, say, your laptop underneath. This is especially true if you’ve set the grille (which is adjustable) to aim slightly downwards, which you probably would do if it was above eye level. And the fan is quite powerful enough to project the drips forward when they drop.

The ambient humidity in the room where I did the test was about 43%RH. The Chillmax sent that up to nearly 58%RH. The drop at the end is where the water ran out, and it is likely that it would have settled around 60%RH. And that was why the air coming out of it feels softer – it’s more humid than the air being sucked in. When you turn the Chillmax on, you can actually see the vapour in the right light – it’s basically fog.

It’s this raised humidity of the cooled air which really brings into question whether the Chillmax is worth the investment. Most people will know that you can have a hot summer day in the high 20s where it is comfortable and pleasant, and another – perhaps slightly cooler – one which is really sticky and sweaty. That’s because of the humidity, or water vapour in the air.

The amount of water vapour that air can hold varies with the temperature. At very low temperatures, air might only be able to hold a few milligrammes of water per kg, but at higher temperatures this can go up to nearly 100g per kg of air. People generally refer to this as “the humidity”, but the important measurement – and the one people are probably referring to without realising it – is the relative humidity (RH). This is the amount of water in the air expressed as a percentage of the maximum amount it could hold. When the RH hits 100% (more or less the dew point, though there’s a bit more to it than that) at any temperature, then any additional water will condense out immediately. It’s why your car windscreen fogs up in winter as soon as you get inside, because the air is already close to 100%RH and your breath and perspiration immediately causes the dew point to be exceeded. But even below the dew point, you can still get some condensation if there are nuclei which promote it (such as data loggers and the grille on the front of the Chillmax). But the most important detail in all this is that at higher temperatures, high RH is uncomfortable.

The real issue with evaporative cooling comes with changes of temperature when it is already humid. If it is 30ºC outside and 90%RH, dropping the temperature by 3ºC will send the RH up automatically – possibly hitting the dew point there and then. But if you are adding another 500g of water (which is how much the Chillmax holds when you fill it up), and as my data logger showed, you’re pushing the RH up by at least another 10%. On a hot and sticky day, and with the air unable to hold any more moisture, you’re likely to notice dampness when using the Chillmax (I noticed it even in this test). And as I have already mentioned, when the RH is high evaporative cooling from your sweat is less effective, so you would actually feel more uncomfortable even though the air is a few degrees cooler.

Proper air conditioners remove water from the air they cool – so much so that the best ones have humidifiers in them to stop the cooled air from being too dry. In my car, for example, if I have the A/C on the lowest temperature setting my lips start to feel sore because they’re losing moisture, and other people say that it dries their hair out. Proper A/C units use a special refrigerant the same as you get in fridges and freezers, and they cool the inlet air so much that the RH goes beyond the dew point and most of the water condenses out – that’s why you get a pool of water under your car if you stop with the air conditioning turned on in humid weather (or have problems with them icing up if they’re badly drained). It’s also why it is nice and comfy inside an air-conditioned car (apart from your lips) when it’s hot and sweaty outside, even if you have your A/C set at a normal temperature rather than deep-freeze mode most people use. Dry air feels crisp, whereas moist air feels… well, softer. Almost like a sauna if it’s hot enough. The Chillmax does the opposite of normal A/Cs, and adds moisture.

Aesthetically speaking, the Chillmax is a cube – more or less – about 15cm along each side. There are two buttons on the top rear, one which changes the fan speed to one of three settings (or off), with a blue LED for each, and another button that turns the night light on or off. There’s a flap on the top front through which you add the water. The radiator system is a plastic-framed insert which you access by pulling the front grille out. It slots in and out easily. You can’t replace the fibre inserts in the radiator (well, I think you could if you could get hold of them), but you can buy the whole radiator assembly from JML for £15. My only major gripe is the power cable. The jack plug that goes into the Chillmax is quite stubby and doesn’t go into the socket very far, so it is easy to dislodge it. However, the cable itself is quite long, and the  mains plug is a moulded UK type.

JML claims the Chillmax can run for up to 10 hours per fill, but this is undoubtedly on the lowest of the three fan speeds. At top speed, it runs out in less than three hours. To be fair to it, you do still get a noticeable cooling effect on the lowest speed, and since the water lasts longer then, less of it will be getting pumped into the air at any one time, and that might offset what I said about humidity very slightly – but it’s still being pumped out.  JML sells the humidification as a positive without relating it to the comfort relationship between temperature and RH, but note what I said above. If you want to cool down in humid weather, it probably isn’t just the temperature that needs to come down, certainly not a mere 3ºC drop, and definitely not if that means pushing high humidity even higher.

Update #1: I have now tested it in what I considered to be hot and sticky conditions – the kind of weather that means you’re sweating even when sitting still.

Here’s the temperature log (red line again shows the switch over between desk fan and Chillmax.Chillmax - temperature log in hot and sticky conditions

The Chillmax still achieved a similar temperature drop to the initial test. However, the air did not actually feel any cooler blowing on my face. If anything, it was more uncomfortable, though this is a subjective comment. The graph for Relative Humidity below explains why.

Chillmax - RH log in hot and sticky conditionsThe ambient RH was similar to last time, but the Chillmax sent it up to about 70% (a larger jump than in the first test). This is why there was no noticeable improvement in comfort – the small temperature drop was cancelled out by making the air much more humid (i.e. sticky).

You might find the Chillmax useful. It’s quite a smart little device – it’s not a Rolls Royce build, but it’s not badly made for what it is – and not that noisy (but you can hear the fan on the top speed). It certainly cools the air. A little, at any rate. Unfortunately, the increase in humidity that goes along with that cooling definitely seems to cancel it out out at higher temperatures.

Update #2: I tried it in the latest heatwave (33ºC outside on 23 July) and you can’t feel any cooling effect at all.

Update #3: Right! That’s it! That “latest heatwave” maxed at 38°C indoors on 25 July, and even now – 1am on 26 July – it’s 36°C at 50%RH and I feel The Devil biting my ass. The last thing I want is to send the RH up to 90% using the Chillmax to get the temperature down to only 33°C. God knows how I’m going to sleep tonight. So I have a proper air conditioner arriving tomorrow – watch out for a review of that.

Does it really work?

Well, it does cool the air by a few degrees, but it also sends the humidity up. So if it is already humid and sticky, the cooling effect is completely cancelled out by the extra stickiness. You might get away with that if your windows are open and there’s a through-draught in your house (or personal space), but if it’s also very hot you may not see any benefit at all.

It definitely doesn’t do what you might think it does from those TV ads. It would be fine if it just cooled, but the fact that it also humidifies is the main problem you’re likely to experience.

From my own use of it, I would say that it is a better humidifier than it is a cooler – especially when it is very hot, which is the last thing you want.

Will it cool more if I use ice water?

No. Evaporative coolers are not influenced significantly by the temperature of the water used in them. The temperature of the air that comes out depends on the temperature (and humidity) of the air going in, and the science of evaporation.

Can I use it to cool my PC?

Someone found this article on the search term “jml chillmax air for pc cooling”. If they mean what I think they mean, no, there is absolutely no way you want to be blowing damp air into your PC.

They might have meant powering it from a PC. The mains adapter is rated 5.0V at 1.8A, so assuming the Chillmax does draw 1.8A (and it probably doesn’t, as this is the maximum rating of the adapter) then your PC couldn’t supply that current from a USB port. USB ports are rated at 0.5A or 0.9A depending on the type. Dedicated charging USB ports can handle up to 1.5A, and although that’s a close call (the fan in the Chillmax looks like a computer fan), personally I wouldn’t risk trying to power it from a PC.

Can you get larger versions?

You can certainly get larger evaporative coolers. The working principle is that the larger the surface area of water, and the greater the airflow over that water, then the greater will be the possible drop in temperature at the front end. However, cooling effectiveness is influenced greatly by the RH of the air going in.

If the air is very dry, then a large evaporative cooler might be able to drop inlet air at 30ºC down by as much as 10ºC. However, if the inlet air is very humid, the temperature drop could be as little as 1ºC. In the UK, the realistic temperature drop you could expect on a non-humid day for a large cooler would be around 5-6ºC, but on a sticky day you’d only get about a 3ºC drop.

Suppliers of these devices say that they need good ventilation or extraction, and I would imagine that’s so the humid air can escape. If you’re evaporating more water to get better cooling on larger devices, you’re also producing a lot more water vapour.


I originally posted this article in October 2015, shortly after I started using PayPal Here to take card payments from pupils. Before then, I’d been using iZettle, but I had an unfortunate experience with them which forced me to find an alternative. They eventually admitted they were in error, but it was too late and I had purchased and started using a PayPal Here card reader.PayPal Here card reader

Since 2015, I have taken more than £70,000 in card payments through PayPal Here. As time has gone by, the number of people paying me by card has increased, and right now I’d say that about 90% of pupils pay that way. The rest still use cash (occasionally, someone will block book and hand over up to £700 in notes), and a few use bank transfers (block bookings sometimes come in this way). I refuse to take cheques – if someone has a cheque book, they have a card, and I can read that instead.

The PayPal Here reader can carry out transactions via contactless, PIN, and swipe (though swipe is not necessary in the UK). Single hour lessons can be paid using their card by contactless (if pupils have them) but anything above £30 by card has to be by PIN. Contactless phone apps depend on the app they’re using, and many pupils use these to pay several hundred pounds with no trouble.

Since I began using it, PayPal has updated the app several times, and it is extremely convenient being able to sign into the app using my fingerprint these days.

The massive benefit of PayPal over iZettle is that the money from a transaction goes into your PayPal account instantly. When you transfer it from there to your bank account, for all practical purposes that is instant as well (it says it can take “up to 2 hours”, but less than a minute is typical). iZettle took nearly a week most times – and we’re talking a business week here, so Bank Holidays both here and in Sweden (where iZetlle is based).

How long do PayPal Here payments take to clear?

For all practical purposes, they’re instant.

When you take a card payment either by chip & PIN or contactless, funds are instantly transferred to your PayPal Here account. You can leave them there, or transfer them to your bank account whenever it suits you – either from the app or from PayPal on your computer.

My only minor gripe is that you have to transfer the money manually – you can’t set it to go straight into your bank account. It’s on my wish list.

How much does the card machine cost?

Under £50 right now – often less if they’re doing an offer. I have three of them as a result of offers just so I have backups, though I am still on my first reader.

Is there a monthly rental fee?

No. You buy the card reader outright and only pay a fee per transaction.

How much do they charge per transaction?

It’s 2.75%. For each £25 lesson paid for by card, you “lose” 69p.

PayPal takes 23p for each £1 you take


I saw some clown state this recently, and it’s bollocks. On a £25 lesson, the fee is 69p.

Other card reader vendors have lower fees

I’m not saying you must use PayPal. Just be aware that other vendors’ fees are often on a sliding scale (iZettle’s was),  and you only get the lower rates if you take more than a certain amount per month – which for an ADI is often quite high. I triggered iZettle’s lower rate fees a couple of times, but the lower rate only applies to takings above the threshold.

For example, if there is a threshold at takings of £5,000 per month, and you pay 2.75% up to that, and 2.5% above it, then if you take £5,500 in that month, you pay 2.75% on £5,000, and 2.5% on £500. To get any real benefit, you’d need to be taking £10,000 per month or more. Small multi-car driving schools might benefit, but a self-employed ADI wouldn’t.

SumUp has a fee of 1.69% per transaction. Yes, that’s less than PayPal’s fee. In a typical year, with SumUp you’d be paying £634 in fees. With PayPal you’d be paying £1,030. I like PayPal (and a lot of pupils use it anyway), and think the extra I pay is worth it. That’s just me.

Some vendors have no fees

And they keep the money longer to get interest on it to cover their costs or charge a rental fee. There’s no free ride when it comes to clearing card payments, and someone somewhere pays for it.

The charges are a rip off

Fine. Keep taking cash.

You’re not going to get away from transaction charges if you also want a decent service. A fee of 69p is nothing on a £25 bill. All you have to do is increase your prices slightly and you’ve covered the fee, anyway.

But I can save money if I don’t have to pay transaction fees

As I say. Fine. Keep taking cash. You probably also believe your car isn’t an overhead because you own it (it is), and that if you don’t have to pay a franchiser then you’re better off by the whole franchise fee (you’re not). A card fee is an overhead, that’s all.

I can’t see the point of taking card payments

Fine. Keep taking cash. It does seem to be the older ADIs who think like this, though.

For me, from the day I first became an instructor, the ability to take card payments was on my wish list. As years went by, having to carry lots of cash around (sometimes, a heck of a lot) and dozens of cheques – and make frequent trips to the bank – was becoming a major headache. Bank branches, especially convenient local ones, are an increasingly endangered species, and with parking fees and lost lesson time, and cheques (which are useless to you until they’re banked, and some weeks, every pupil would pay by cheque), it was more like an atomic migraine than a headache. There is a business cost associated with that, which is proportional to how often you have to go to pay money in. With cheques especially, I’d only have a cash flow if I went to the bank. I’d been waiting for something like PayPal Here or iZettle – and there are others – to appear, and got in on the ground floor.

What about cheques?

What about them? No one has attempted to pay me by cheque for at least 4 years now (though they only did before because it was either that or cash). A couple of new pupils have asked initially if I take them, but when I point out the card machine and the fact that everyone has a card even if they have a chequebook (otherwise cheques are pretty useless), it’s never mentioned again.

I can take pupils to a cashpoint

Good for you. I, on the other hand, don’t need to. The card machine becomes the cashpoint, so it’s more convenient for me and more convenient for them. And that is certainly not going to affect their opinion of me in a negative way. Of course, if I insisted on frog-marching them to a cashpoint… who knows what they might think?

Is it of any benefit to take card payments?

As I said, it has saved me a lot – in monetary terms, and in terms of my sanity.

But another benefit is less tangible. Some pupils might be impressed if you pull out an iPad and have a glitzy demonstration video to get some point across. Believe me, many more are impressed when you tell them you can take card payments – even more so when you actually take a payment in front of them and they get an instant texted receipt. This might become less true in the future as the dinosaurs gradually die out, but right now it works in a highly positive way.


Privacy button on keyboardI’m being driven to distraction by the number of emails from sites I’m subscribed to either asking me to confirm I still want them to contact me (there were a lot of these when GDPR first came in), or telling me that they’ll still contact me unless I tell them not to (the more recent, and far more sensible, approach). To be honest, I’d just prefer it if they left things as they are and didn’t keep telling me about it, but everyone seems afraid of GDPR and they feel they have to do something – even if “something” is a fantastic pain in the arse.

The worst approach, though, is how an increasing number of sites have simply blocked European visitors.

The main culprits seem to be American food sites and blogs. It’s perhaps understandable when you consider the kinds of people who run them, but it’s still annoying now that simple Google searches throw up links that you can’t visit. It’s like we’ve gone back to The Dark Ages.

Well, I don’t like that one bit. Getting round it is easy, though. All you need is a VPN client. Fire it up, and you can pretend to be in any country in the world. I just pick an American server location, then refresh my browser, and the blocked site loads up normally. It also works when you get one of those “this content is not available from your location” messages on YouTube or other sites carrying broadcast items (MSN can be very irritating when it feeds you a link, then won’t let you see it when you click it!)

Incidentally, a year or so ago, there was that kerfuffle involving a British celebrity who had obtained an injunction so that his name could not be seen by anyone in the UK concerning some domestic issue he was involved in. It was a bit of a joke, because every other country could print it unrestricted, so finding out who it was would be easy for anyone who had contacts outside the UK (a large percentage of the population, I would imagine). Indeed, it was on many forums in black and white, though posts were quickly removed in some cases. At the time, I was curious, so I fired up the VPN and simply looked at some foreign newspapers to find out who they were talking about.

The client I use is called SlickVPN (I get it as part of my Usenet subscription).


Audacity main windowI don’t know about you, but I find that people are rubbish at leaving coherent voicemail messages. If they’re not rubbing the phone around their head making crackles and thumps, or blowing into the microphone so it sounds like they’re standing in a Force 9 gale (this is right up there with whistling on the annoyance scale for me), they’re mumbling or stumbling over their words. Many important voicemails come from people wearing headsets, and while these tend to be quiet at the best of times, clarity is often worsened by the user touching or adjusting the boom while they’re talking.

The result is that you have to listen to the message several times to extract the information, and even then it’s sometimes hard picking out details like phone numbers or other numerical details.

I had an important message last week which was definitely going to need several listens. The speaker was talking very quickly, and the nature of the call meant she was back-pedalling and stumbling over her words. Calling back wasn’t an option since they never answer calls directly, and this voicemail was already their response to an email I had sent (not replying by email, so everything is there in black and white, was another example of their back-pedalling). So it occurred to me that it would be useful if I could save the message indefinitely on my PC. I could then process and amplify it, and use decent headphones so I could hear it properly.

One way of doing it would be to use a 3.5mm jack cable between your phone’s headphone socket and your computer’s soundcard line-in. Except many phones these days use the USB port for the headphones (mine is one of them), and the way they use it is non-standard and isn’t guaranteed to work with audio devices the way you’d expect (mine is one of those, too). I wasn’t in the mood to start playing around with USB cables, so I looked for a different way.

On a Windows computer you can use something called loopback, where you effectively tap into the audio signals that get sent through your soundcard. All you need is an app to play your voicemail – like Skype – and suitable recording software to grab it.

My favourite sound recorder is Audacity. I use it to edit and enhance recordings I make at gigs, and it’s open source – which means it’s free (I’ve donated). Assuming you have installed Audacity, all you need to do is set your Audio Host to Windows WASAPI and your Audio Device to Speakers (Realtek High Definition Audio) (loopback). That last one might be different on your machine if you have a different soundcard driver.

My phone is on EE, and if you dial 07953 222222 from another phone (or Skype), then enter your mobile number and password, you can access your voicemail.

And that’s it. Dial in to your voicemail, set it playing, then click the record button in Audacity. Once you’ve captured it, Audacity lets you trim off the lead-in and -out parts so you’re left with just your voicemail message. You can make it louder in various ways, but the simplest is to select Effect >> Normalize… and apply a setting of about -2.0dB. You can save your file in various formats – MP3 if you’re not going to adjust it any more (small file) or WAV if you are (bigger file).


Ford Focus oil change messageThis article was originally written a few years ago, but it has become extremely popular, and gets hundreds of hits a week.

The original article refers to all Focus models between 2016 and 2018 (not the latest model). The reset procedure is different on the 2019 Focus, and be careful with that because there may be an issue with the latest model that Ford is being very cagey about (see later). Also note that this applies to other Ford vehicles – it’s Ford’s software system rather than specific models of car which is responsible.

It all began back in 2016, when I got a message on my brand new Ford Focus TDCi Titanium centre display telling me that it was due for an oil change. I wouldn’t have minded, except that it was only on 5,500 miles and my official service points (set by my lease agent) are every 12,500 miles.

I spoke with the local dealer and they said just to book it in so they could reset it. I wasn’t too keen on that, since visits to the dealer inevitably mean at least half a day in lost lesson time.

I didn’t for a moment think it was anything other than an erroneous message. There is an oil warning lamp on the dash which I would never ignore, but centre display messages are a different matter entirely. I mean, how many of us have been driving up a 40% slope only to be advised to change the gear to 4th, 5th, or even 6th? The car just won’t do it. Before I quite realised this, my first action was to buy an OBD II monitor tool so I could check/reset the message myself, but the OBD found no faults, and there was nothing to reset. I should have realised this – and the oil change warning remained stubbornly visible.

Then I did what I should have done in the first place and Googled it. It turns out Ford has a system which gives an oil change warning at various points based on how it thinks the car is being driven. No fault is logged, since the trigger is software-based and is “calculated”. Apparently, you used to be able to set different trigger points manually (in America, at least), but there is no such option in the UK that I can see.

Since 2016, and across at least four other Focuses, I’ve had it come on at as low as around 1,000 miles, and at other silly points shortly after a service. None of my pupils (or me) drives it that badly, of that I’m certain.

How to reset the oil change warning

Resetting it is incredibly simple (pre-2018) – though completely undocumented by Ford. All you do is:

  1. Turn on the ignition (or push the start button with the clutch up)
  2. Press the brake and accelerator fully down

After a moment, the centre display will tell you that the reset is in progress. Keep the pedals down until it informs you that reset is complete. No more oil change warning! From what I understand, this applies to all Focus models from MkII up until the last of the pre-2018 models.

Does this work on other Ford cars?

You’ll have to try it and see. Logic would dictate that Ford has implemented the same procedure on all its current (pre-2019) vehicles. However, when you consider Ford’s indexing system at the back of the User Manual, logic isn’t something they seem to waste much time on, and there’s every possibility that the reset procedure is totally different on other models. If you try it and it works, drop me a line so I can add it here.

I am told it also works on the Ford Fiesta and C-Max.

Does it work on the latest (2018) Focus?

No. Resetting the oil on the new model is done through the settings page on the information console (this is how it ought to have been on the earlier models). You simply scroll to the little cog symbol, then select Information, then scroll down to Oil Life. Press and hold OK and it resets after a few seconds. Mine came on after 3,900 miles!

However, be aware that many people are experiencing the problem in the new (2018) Focus. The dealers are playing as ignorant as ever, and Ford as secretive as ever, but piecing information I have received from readers together there may be an issue with the 2018 Focus where the oil change warning ought not to be ignored.

Can you turn the warning off?

You mean so it doesn’t happen again? No. Damn Ford! All you can do is reset it each time.

How soon should I get my oil changed when the warning message comes on?

For a Focus, if your car is under the manufacturer’s warranty then I think they allow 1,000 miles on top of the normal service points (but check that with your local agents). My lease company allows me the range of 11,500-13,500 to book it in for a service [note: service points were every 12,500 miles up to 2018; they are at 10,000 and 20,000 miles on the latest 2018 models]. Whatever your local agent allows, outside of that might affect your warranty, so I say again: check with them before assuming anything.

Of course, if the oil change warning message appears before 12,500 miles (or whatever your service points are) then you can safely ignore it (or reset it, as explained above) in the pre-2018 models. It isn’t a sensor warning, just a software-based calculated value. If the oil warning dashboard light comes on, though, you mustn’t ignore that.

Note that the 2018 Focus may have an issue, so be careful if you ignore the warning.

You shouldn’t ignore the message because you could damage your car

Someone wrote to me making this point (and that was in 2017, so the previous model). As I have explained above, the alert (it isn’t a warning) is calculated based on how the in-car computer thinks you’re driving. Frankly, when it comes on at around 1,000 miles when you’ve only had the car a few weeks, or several days after it has had a service, and the oil definitely isn’t old, yes you can ignore it. Having said that, read the update at the end of this article relating to the 2018-onwards models (between the lines, there may be an issue that no one at Ford is revealing).

My lease agent sets the service points at every 12,500 miles (pre-2018 models). They will not allow me to have it serviced any earlier (±1,000 miles). I know that Ford talks of 7,500 mile service points, and that’s fine. If you have a private vehicle then follow their advice. But if the warning comes on at any other time before that you can safely reset it – if nothing else, until you can get it in for its service.

However, note that the 2018 Focus has service points at 10,000 and 20,000 miles, and there may be an issue with oil degradation, so be careful if you ignore the warning.

My Ford won’t clear warning messages

It depends which message you are referring to, but if there is an underlying problem, cancelling a message is no good because it just comes back. It’s like the empty windscreen washer message – you can OK it, but it comes back again unless you fill the washer bottle up.

However, there could also be a sensor fault, or a fault with the software, in which case it needs fixing. If you can’t do it, it needs to go to a garage.

Update 10 April 2019: I have heard from an instructor who is with the AA that they’ve been told not to reset the message if it comes on with the 2018-onwards vehicles (the latest model), but to book it into the dealership. My own lease agent hasn’t said anything.

I must say that this would be extremely annoying, as my personal experience of my dealership is that even when there is indisputable video evidence of an intermittent fault occurring several times, they will still insist of having it in for a full day, then not find anything wrong (even though it was obvious they wouldn’t because of what “intermittent” means), and then want it back again the next time it happens. Every lost day costs me up to £200 in earnings.

They did it when I had the floppy clutch pedal problem last year. It turned out to be a known issue with one of the cylinders, and the engineer actually witnessed it sticking down, but they still wanted the bloody thing in, did a namby-pamby hydraulic fluid bleed, then had it in for another day when that didn’t work – which I discovered about an hour after taking it away the first time.

Right now, Sync3 has a habit of freezing (though as of April 2019 there is an update which fixes that). Judging from the Google results on that, it is another known issue. I have videoed the damned thing in its frozen and unresponsive state and shown it to them at the dealership. And… they want it in for a full day to test it. Aaargh.

Update 12 May 2019: Another reader tells me that their dealer has suggested there is a problem with the latest Focus engines and “the oil degrades”. Personally, I cannot see how the oil – synthetic motor oil – can degrade ten times faster than it should, but be aware of this if you have a 2018-onwards Focus.

Update November 2019: A reader who had experienced this and had to keep taking his car in has recently told me that the Ford garage eventually informed him that there is a non-safety recall for the problem, and that it is a software issue, requiring an update.

Disclaimer: I take no responsibility if an oil change really is needed and you ignore it – especially in the new (2018-onwards) Focus, which may have an issue that Ford isn’t letting on about.

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