Originally Posted by corbett_auto
hmmm, interesting problem. My first thought is that the temperature sensor is bad. Not the one for the engine but the one that measures outside temp. Does the car have an automatic climate control? Does it show you the outside temperature? Pay attention to what it reads, if it is giving a far off reading that is the problem.
My 98 Gran Prix did something very similar to this a few years ago. The sensor is not very expensive and is easy to change. My was located on the radiator support.
No automatic climate control. I'm starting to think the switch in the dashboard/console that regulates the speed of the blower is the culprit. I'm trying to figure out how to get that apart easily to see if that's what's doing it and possibly running a jumper wire to see if that's what is the problem.
Since it's complaining whether I use the A/C or the heater and it's working sporadically, I'm assuming a worn or loose connection.