Home / News / The Unusual Object on Your Automobile’s Dashboard? The device is a sunload sensor. This serves its intended purpose

The Unusual Object on Your Automobile’s Dashboard? The device is a sunload sensor. This serves its intended purpose

Contemporary automobiles are replete with remarkably clever engineering, much of which often goes unnoticed. Consider, for example, the small chips on your car’s windshield. These chips are found on almost every vehicle, but unless someone specifically draws your attention to them, they are practically invisible to us due to our lack of attention.

Equally, if not more nuanced, is the solar, or sunload, sensor. The feature is typically a small, circular protrusion located at the rear of your dashboard. Its appearance may vary, with some being circular and others not, and some being raised while others are flush with the surface. However, rest assured that it is present, even if you have never observed it before.

According to Auto Service World, a Canadian automotive aftermarket industry magazine, sunload sensors are typically positioned at the upper part of the dashboard and are commonly attached to a detachable plate, speaker grill, or defroster vent. “There is typically one on each side of the dash to account for variations in sunlight exposure.”

However, what is their purpose? Predictably, the purpose is to monitor the amount of sunlight penetrating the interior of the vehicle. However, the reason behind this may be somewhat surprising. The purpose of this sensor is not, as one might assume, to monitor the brightness of the external environment, such as for activating automatic headlights or adjusting the brightness of the dashboard display during the night. We are aware that there is a separate sensor for that, but this particular sensor serves a different function.

Instead, the sunload sensor is a component of the climate control system.

According to Auto Service World, sunload sensors are used to measure the strength of sunlight and modify the HVAC control system in order to enhance the comfort of the driver and passengers during sunny days.

The fan speed may increase, and the blend doors may open to enhance cooling in bright sunlight conditions.

In general, these sensors operate by utilizing a photodiode, which is a semiconductor diode that converts photon radiation, such as visible light, as well as other forms like infrared, X-rays, and gamma rays, into electrical current. Nevertheless, when the intensity of light rises, the resistance of the diode also increases, leading to a decrease in the number of volts that reach the car’s internal monitoring systems from the sensor.

Functioning smoothly and efficiently, the control module interprets the decrease in voltage as a cue to enhance the performance of the A/C systems, preventing the driver from experiencing the dreadful outcome of overheating inside an SUV.

And as anyone who has experienced being trapped in a car with a malfunctioning HVAC system can attest, this statement is not an exaggeration. According to Auto Service World, sunlight entering the vehicle can account for up to 60% of this heat load, making the sunload sensor essential for managing the interior heat load of a vehicle.

Put simply, the absence of this small blob on your dashboard could result in your car absorbing up to two and a half times more heat. Whew!

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