Although with the fury of bringing screens to cars There are fewer and fewer buttons, we still find a lot of old-fashioned controls scattered around the steering wheel and the dashboard of the car. However, there is usually a small element (sometimes shaped like a circular knob, which may or may not protrude) that usually looks like a button that goes unnoticed due to its location: it is far enough away that it cannot be easily operated. Spoiler: if you touch it nothing happens.
And nothing happens simply because it is a solar sensor or solar load sensor (if we get more technical, a phototransistor), a piece little known to the general public but of great importance as it is the element that the automatic air conditioning uses to regulate the temperature correctly.
It is essential to control the temperature of the car
More specifically, is located at the bottom of the dashboard and in the central area, attached to the front window. It usually has the speaker grille or the air outlet grille nearby to defog the window. Hence it neither looks good nor is it comfortable to touch. That position makes all the sense in the world: it is one of the best areas inside the cabin to capture sunlight from outside.
Precisely the reason for the sensor, since the sunlight that enters a car can reach represent up to 60% heat load that the air conditioning system has to overcome in the search for comfort. A good everyday example: the temperature difference between parking in the same place on a summer day when the sun is shining overhead or doing so at night or when it is cloudy.
This solar load sensor It is actually a photodiode which measures the intensity of solar radiation in order to be able adjust climate controlwhich includes the heating, ventilation and air conditioning system. On that hot day in the example, the air conditioning will have to work as hard as possible to cool the cabin as soon as possible. But if it’s night or cloudy, you won’t need to blow as hard.
At a technical level, its mechanism is simple: the photodiode moves in an operating range between 0 and 5 Volts, offering more resistance as the light intensity increases, so that the sensor signal decreases as the solar load increases. This signal is what then reaches the control, which gives orders to the system to adjust the speed and intensity.
The solar load sensor is not the only one responsible of the operation of the air conditioning, since the vehicle integrates more sensors such as the sensor to measure the interior temperature. And they also have other sensors to turn the lights on or off or configure the mode of the screens and dashboard depending on the exterior lighting.
By the way, in some cars there is not only one solar charge sensor, but there are two, one on each side of the dashboard and in that same area adjacent to the front window: they are models that have dual zone air conditioning.
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Images | Skoda, Opel and SEAT
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