what the heck is the sensor called, like what do i tell the guy at the counter what i am looking for?

Yes, it could affect how the heater works. If it sees the outside temperature as 137, the HVAC system won't see a need to add heat to that. The cost at the dealer may be around $23. Ambient Temperature Sensor / Switch HVAC Ambient Temp Sensor part #16169194

thanks. which should i go with? i found one from gmpartsdirect.com here http://www.gmpartsdirect.com/results.cfm and there is another one from rockauto here http://www.rockauto.com/catalog/raframecatalog.php.

This is what you need.

http://info.rockauto.com/ACDelco/Det...l?15-71823.jpg
http://www.rockauto.com/catalog/x,ca...,parttype,7000

I know this is an old post, but I just ran into the same problem.....exterior temp reads 140F and heater doesn't want to warm. I cleaned up the connectors on the sensor and am getting a 50F reading in my unheated garage....that'* close to the outside temp....and will pick up a sensor on my way home tomorrow if it reads erratic. Thanks for the tip!