Heater Control not working?

YOURMAMA1975

MEMBER
1999 GMC YUKON
5.7L
V8
4WD
AUTOMATIC
126,000 MILES

I just recently had my dash apart for a separate reason. The vehicle listed above is an SLT. I replaced the heater core and heater fan because they were bad. All wires plugged in. The problem is, my blend and heat/cold control knobs, recirculating button and A/C buttons do not work. The fan control does work. It feels like it is blowing about 60° to 70°when on and engine is warm. Could this be the heater control panel itself? I'm getting ready to order one, but I would like an expert's advice because I can always return it if it's something else. Any help would be greatly appreciated. Thank you

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
42,904 POSTS

It could be the HVAC control module, but we should check the G202 ground on the right side of the dash. Also check the fuse #12 for power. here is a guide to help and the climate control wiring diagrams so you can see how the system works:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Also included is how to change out the HVAC controller in case you need it. Check out the images (below). Please let us know what happens.

Images (Click to make bigger)