Temperature sensor

[GT1975]

The outdoor temp sensor on my GMC drives me nuts. The software does not take a reading often enough. If I start the truck early in the morning and the outdoor temp is 70 for example, and take a short trip and then later start the truck again, it still believes the outdoor temp is 70 when in fact it is 95. The false temp forces the AC to stay off or provide very limited cooling unless I turn the stat down as far as it will go. Why???   Why can’t the system take readings each time the truck is started?

[Doug_Scott]

You sure the ATC even looks at external temp?  It should be reading internal temp and cooling based on internal temp compared to desired temp. External temp is not really an issue. 

[reardiff]

Funny you mention this I have been thinking the exact same thing in my 2017.  It can read the same outside temperature for hours at a time when it's clearly not right. Like you said back out of the garage it may say 72, drive around for a few hours going to a few stores and now it's 90 and sunny outside but still says 72.   But other times it seems Ok. 

 

For example went up pikes peak recently and I watched it drop like a rock most of the way up from the 70's into the upper 30's, worked just like it should.  But then just last week it was stuck at 71 almost the entire day when it was close to or even a little over 90. It works when it wants to..

 

[Havasubum]

I asked the GMC dealer the same question.  According to them, the temperature sensor won't register until the truck travels at least 45-50mph for a few minutes.  I've verified this explanation several times while we're in Lake Havasu, AZ.

[Doug_Scott]

Have they changed the system on the 2017 compared to the earlier models?  I added the mirror with the compass and the temp along with onstar back in 2011.  Had to add the sensor out ahead of the radiator and run new wires back into the cab of the truck to the mirror.  My temp is accurate, and updates in what appears to be real time. I can leave my house with the temp showing 80, and a couple of minutes later it was 82.