All morning and afternoon my car sat in an outside garage that averaged probably 90F. I took my Prius out to run a couple of errands and the outside temperature read 86F. Since I knew it was around 103 outside I thought this would be an interesting experiment to see how long it took for the reading to correct itself. 10 minutes later and it read 88F outside. 30 minutes later and it read 90F outside. This was a combination of driving and parking in the sun. I have always noted the outside temperature to be fairly accurate, but something seems very strange. All I can think of is that I gave my car a good hand washing a couple of days ago. Can I easily see the sensor and check to see if it is coated with something, etc.? Thanks for any advice.
I had the same problem last week. My gauge had always been dead-on but one day (immediately following a car wash) it was off by 10 degrees or so. It seems to be better now. Where is the sensor located?
If you look through the grill, you can see the sensor mounted to the vertical support in front of the radiator.
So that would mean you need to be moving to get an accurate reading? Seems like if you were standing still and the cooling fan wasn't running, the radiator would be radiationg heat forward and raise the temp at the sensor.
I also noticed my temp. was off after washing it. It took quite a few days for it to get back to normal.
Mine starts off too hot by about 2-5 degrees when I start driving after leaving it in the sun, but it settles down to the correct temp in about 5 minutes.