: heating and a/c system please help

04-07-08, 03:16 PM
ok i live in md and right now its about 45 degrees outside but my outside temperature reads 85 degrees on my car...and i notice when i set my heat on 90 degrees it gets real hot then when i turn it down 2 85 cold air blows from the vents at first cold air didnt start coming out until 75 degrees..can someone tell me wat the problem is?

04-07-08, 04:04 PM
What year-model of car?

You should replace the outside ambient air temperature sensor because some year-model Cadillacs use that information as an input to the HVAC system.

04-07-08, 05:38 PM
Yup, your car thinks it is 85 degrees, so when you ask for 75, it thinks it has to cool to reach that temperature.

04-07-08, 11:05 PM
So how does this happen? With defective out side air temp sensor it defaults to the inside air? Which years, very strange behavior, never heard of it... K_C

04-08-08, 01:06 AM
it iz a 97 deville

04-08-08, 10:18 AM
I believe that the OAT sensor is also linked to the HVAC system. If it is 20 degrees outside and the car thinks it is 95, it is going to cool to reach a requested 75 rather than heat to do it.

04-09-08, 10:42 AM
where is my outside temperature thermonitor located at

04-09-08, 03:26 PM
It's the small black item at the end of a covered wire clipped to the front of the hood latch/radiator support. Single plug with safety catch. New unit is about $14 at www.rockauto.com. BTW, it's a thermistor; a resistor which changes value as temperature varies.