The mysteries of a car's dashboard can be pretty hard to decipher, despite the fact that we're all meant to know everything about our daily drivers.
The reality is that there are always plenty of knobs and buttons that we rarely press, and knowing what all of these individual things actually do can be a real memory challenge.
At least they generally have icons or labels on them - but one of the most rarely-understood parts of any car just looks like a simple little black puck or disk.
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If you've ever noticed a little black disk like this around your dashboard, or perhaps under your windshield, you may have wondered what it does - you can't push or twist it, either, since it's not interactive.
Well, this anonymous little bit of plastic might just be a more important and useful bit of tech than you'd think - it's probably a sunload sensor.
These sensors are placed in a few strategic places around the cabin in many modern cars, and monitor exactly what their name suggests - how much sunlight is making it into the car.
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You might be tempted to think this is so that the car can work out if you need your headlights on, or perhaps to help brighten the infotainment display to make sure you can see it, but you'd be wrong.
Sunload sensors are, in fact, all about climate control - they're part of how more sophisticated and newer cars check that the temperature inside the cabin is comfortable for both the driver and their passengers.
The Canadian magazine Auto Service World explained it back in 2009: "Sunload sensors monitor the intensity of sunlight and adjust the HVAC [heating, ventilation, and air conditioning] control to improve the comfort level of the driver and passengers on sunny days. Bright sunlight conditions can result in the fan speed increasing, and blend doors opening to improve cooling".
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They're actually incredibly simple sensors, too, using a semiconducting diode to measure the ambient light intake by checking its resistance, and telling the car whatever it needs to know via that system.
So, while you might be tempted to think that they're not particularly key to your driving experience, sunload sensors might just be lifesavers.
After all, anyone who's doing a substantial road trip on a sunny summer's day with either broken or faulty air conditioning will know that driving in the sweltering heat can be absolutely miserable - and dangerous.
Sunload sensors help your car to keep things safe and comfortable in the cabin, making them a hidden key to any great driving experience.