Cabin temp regulation
 

03 Tahoe has new dash controller. Automatic climate controls. Now what causes the in cab temp to swing from warm to cool on its own? Is it the actuator itself going rogue or something else?
I have recalibrated the hvac actuators twice now.

Re: Cabin temp regulation
 

The digital heat/AC controller gets cabin temp from a sensor in the headliner over the driver's head. It has a little fan inside IIRC.
It looks kinda like a microphone grille.

Attachment 2185377

There's also a sun load sensor dead centre between the defrost vents on the dash that does double duty as a nighttime sensor to turn on the auto headlights.

If both of those sensors are working properly and the ambient outside temp sensor is reporting the correct temp in your mirror then the HVAC controller may be flaking out on you.

You should be able to get a look at the reported temperatures with an Snap On Verus, AUTEL Maxsys, or Tech2.

Re: Cabin temp regulation
 

I just recently replaced the control panel with a new one from O'Reillys, might be a Dorman. Everything works but when I commanded it to heat it began to warm then turned cooler over and over with the temp setting full hot. Since I've never changed the actuators on this old rig I assumed it might be one going bad. I just couldn't imagine it running back and forth temps own it's own.
I don't have either of those scan tools, just an Innova or something that only reads generic engine codes. When I get it back I will fiddle with it some more. I just had the A/C leak repaired too.
That roof sensor has a little fan doesn't it? Seems like I used to hear it buzz when the radio was turned down. ?