I’m at the point where I completely disregard any car’s outdoor temperature sensor. In hot days when the car’s been in the sun, they seem to all way overestimate the temperature compared to what the weather app says it is.
I get that the sun will heat up the car and since the thermometer sensor is on the car that heats up too. But what stops them adding some protection measure to the thermometer to avoid this, so that we can get accurate outdoor air temperature readings?
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It depends on where the temperature sensor is, however this will only help to a certain point. If a car has been sitting in the sun, not only will the inside of the cabin be warm, but the chassis of the car will be as well, which will heat up any internal cavity (e.g. engine bay) more than the ambient temperature.
Then, you have the potential heat-island effect. If you’re parked on concrete for example, this will get hot when in the sun and heat up the air surrounding your car, *in addition to* your car also being heated by the sun (inside and out).
The TL:DR of it is that unless the car is moving, the temperature sensor is unlikely to be accurate, and even then it’s only an approximation which will heavily depend on where your car is.
Could be the parking lot.
Paved spaces get warmer in the sun (especially black asphalt) and end up boosting the local temperature by a lot compared to a nearby park or field or something.
Weather stations know about these kinds of effects and tend to install their temperature sensors in places that aren’t affected by them.
Where I work we have to calibrate our themometers once a month to make sure they remain accurate. This is because they are used in the cooking and preparing of food.
Bearing in mind that car themometers were probably only calibrated once at the time the car was built, I would assume that the themometers in cars were not that accurate to begin with, and will only become less accurate over time.
Obviously it doesn’t matter so much with car themometers, car themometers tend to go up by a degree or maybe half a degree at a time. Food themometers are often to two decimel points, but that’s because poorly cooked food can kill you, whereas if a car says it is 10 degrees and it is actually 12 degrees it doesn’t make much difference.
Car thermometers only serve one important purpose, which is to warn against conditions where you may encounter ice on the road. They don’t bother too much about summer accuracy.
The sensor has to be exposed to airflow when you drive, so it can quickly detect icing conditions to warn you, and quick reaction is very good if that sensor is used to optimize your air conditioning too.
Problem is, that this place exposed to airflow may be just under the black bumper in front of the car, next to the engine. Very good while moving. Very easy to heat up when still, both by sun heating the area and engine releasing heat to the area. Lack of airflow does the rest, helping the heat to accumulate.
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