Why you shouldn't believe the temperature displayed by your car's thermometer

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As the heat waves are fast approaching (we were still a little sheltered), motorists are preparing to face long hours of driving in stifling heat. However, you must remain vigilant regarding the thermal indications provided by the vehicles. Indeed, the reliability of these readings is sometimes doubtful and quite far from real temperatures. Why this inaccuracy? The reason is purely technical and quite simple to understand.

Thermistors: an unsuitable technology

The thermometers fitted to our cars are based on a fairly old technology (1980s) called thermistor. The latter is very different from traditional thermometers. This device measures temperature variations by analyzing fluctuations in electrical currents. As explained by The Weather Channel and the information site Quartz, this method, generally reliable, presents nevertheless certain limits in the automotive context.

Positioned at the front of the vehicle, often behind or in the grille, these thermistors mainly capture heat emanating from the ground, which biases the measurements. Road surfaces, real collectors of solar radiation, can thus artificially increase the temperatures displayed up to around ten degrees. It is therefore not uncommon to see readings reaching 45°C, or even 50°C, after leaving your vehicle parked in direct sunlight.

Des false temperatures in winter ? Guaranteed slippage

If in summer, a thermal overestimation is not really serious, the consequences can be much more serious in winter. When the mercury is close to zero, a difference of a few degrees is enough to transform a wet road into a particularly dangerous icy surface.

A driver, reassured by an indication of 2° C or 3° C, could suddenly find himself confronted with road conditions that are much more dangerous than anticipated. This situation is all the more worrying as it can induce a false sense of security, leading to underassessing the real risks and, consequently, considerably increasing the probabilities accident.

Rely on your smartphone instead to find out what temperature it is outside, or play it the old fashioned way: listen to the radio. Météo France, RTL, France Inter will always be more reliable than your car. Yes, it hurts a little to know that when you paid full price for your car, especially if you drive electric. Even though modern thermistors are much more advanced than ten years ago, they are still not 100% accurate.

• Car thermistors often overestimate temperature due to their positioning within the vehicle structure.
• In winter, this inaccuracy can cause accidents by underestimating the risk of icy conditions.
• Use sources such as smartphones or radio instead to obtain more accurate outside temperatures.

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