My 2003 GMC Yukon XL - HVAC issues

doc_rich

I have an 03 XL and never had any issues. My ax/heater is now acting stupid in the front. It's dual climate control and the drivers side will blow hot or cold air but the passenger only hot. I replaced my alternator and battery a few months ago but that is the only major maintenance work that has been done. Anyone know what's going on and htf do I fix it? Thanks

imidazol97

Did you turn off the HVAC system with the key ON before disconnecting the battery?

If the AC is OFF, does the electric actuator for the driver side more the door through temperatures from ambient to hot and back? Does the passenger side do the same, or is there no change in the temperature.
The might indicate a jammed door OR malfunction actuator for the temperature blend door for that side.
See picture.

If the AC has to be on for this to be noticed, I'm guessing there might be a low freon cause. In the leSabres and other H-bodies low freon would cause one side of the evaporator to be warm because the freon had already been evaporated on the other side which there happened to have mostly the passenger air going through it. So the driver didn't get much cooling.

Since you have a two-part system, I'm far out of my league for diagnosis. The actuator might be something a backyard mechanic could see not working by taking off the sound shield under the dash and with engine running have someone operate various controls to identify which actuator does what on the front unit.
Since the actuators do fail, it might be relatively cheap to replace.

Check the diagram for parts. Note #16 and 17 are labeled for left and right. Those are the temperature valves. The actuators may, may be #20 and 21. Sometimes these diagrams are misleading.