Thermometers are used in a variety of ways on vehicles, from telling you the temperature outside, to reading the temperature of the engine so that you can avoid overheating. Even though the temperature sensors can be very small, they are a very important part of several systems on your vehicle.
Having the outside temperature showing on your dash is a handy feature and it is an option that is available on a lot of newer vehicles.
Here is how it works: There is a sensor outside of the vehicle, usually behind the bumper cover. It senses the air temperature outside and sends that signal to the vehicle's computer to display on the dash. These sensors work best when you are traveling down the road and the outside air has a chance to circulate around the sensor.
Sometimes the temperature reading is inaccurate on your dashboard. When you get inaccurate readings, it is usually because the air around the sensor is hotter than the air temperature outside.
For example, if you were stuck in traffic, the temperature of the street can easily be over 120 degrees on a summer day. That heat is radiating up under your vehicle so the sensor is going to think that it is well over 100 degrees outside, when it might actually only be 90 degrees or so. Once you get moving down the road, the temperature tends to drop because you have air flowing over the sensor once again.
The outside air temp senders and their wiring can also be damaged by road debris coming up and hitting them and that can make them send a bad signal to the computer. When that happens, the temperature that is displayed on the dash will not be accurate. Having a mechanic check the sensor out is usually the best way to find out for sure if the sensor is in good shape or if it needs to be replaced.
There are other temperature sensors under the hood and they monitor things like your coolant temperature and even the temperature of the air going into your engine. If any of those sensors go bad, it can make your car run rough, which causes bad gas mileage and could even cause it to break down.
So if your vehicle is running rough and you are getting bad gas mileage, don’t assume that you need a tune-up or new spark plugs. It could be a little part like a temp sensor that’s causing you all that trouble.