I'm having the same problem as Flash did a few years back.
I have changed the sensor, changed the connector and cleaned ground connectors in the engine bay.
I still have erattic ambient temp readings:
1. sometimes the reading will drive down to 15F or so and then slowly climb back up to about 15F below the actual ambient temp.
2. sometimes the ambient reading will settle around 50F and stay there.
3. sometimes it actually does read the true ambient temp.

Any ideas as to the next step greatly appreciated.

 

Where is the ambient air temp sensor in the egine bay, My temperature is consistently 10 degrees below where it should be. Can anyone post a pic? Thanks.

 

It is located on the radiator shroud at the lower front right (passenger) side

 

"A faulty outside air temp sensor"

GM Part # 10248414 is aprox. $10 from the dealer and just plugs in.

The sensor is located on the right (passenger) side of the car, on the outside of the frame rail in the very front by the headlight.

It is held onto the mounting hole on the frame by a plastic push-in clip.

Just pull the clip out of the hole on the frame, release the plug for the wire (the plug has a release clip, pry up on the clip and the plug will release).

Then just put in the new one and you will be in business - it takes a few minutes of driving for the sensor to start reading the outside temp - you have to be moving.


The sensors are either resistance temperature detectors (RTD's) or Thermistors. The resistance of the sensor changes with the temperature.
If you have any corrosion in any of the associated connectors it will increase the resistance that the climate controls is reading.
The resistance across the two sensor wires could be almost infinity,
in that case your display would read a low temp.

Once the old sensor is removed, the HVAC defaults to 69* and will let the AC turn on.

 

Yep that part is actually in the owners manual under Climate Controls/Sensors. It needs to be moving over 20mph for a duration of 2 mins or something like that, before the temp will update. I ran into this one day at the track. Arrived on a cold morning. In the afternoon, it heated up alot outside, but the temp never updated and I couldn't get AC. One lap down the track and return road was not enough to force an update.

 

....all you have to do, is simply remove that bad sensor....and the system automatically defaults to 69 degrees..then, drive the dang thing 2 miles..and then your AC will turn on! THEN! go buy that new sensor!

 

Mine defaults to 54F

 

Same problem here - 1999 Coupe... Gotta find the sensor - I have a new one on hand... Going to photo-document & post to my site - hopefully can add to the sticky / how-to's for next person that has this issue

 

Open the hood. Stand in front center. Look into the opening between from bumper and hood about 18" left of the center line. You will find the sensor at the bottom of the radiator shroud. Gently pull up to release from the plastic friction bolt. Replace sensor. Reinstall.