Rear hvac temperature control works slowly/intermittently

[SnowDrifter]

Been like this for a while now.... But it needs to not be like that.

Issue is this: the rear temp control doesn't change immediately. However, I can set it to all-hot or all-cold and days/weeks later, it'll finally pop over. Issue presents the same behavior whether using the front OHC controls, or rear controls.

I have codes B0429 and B0434.


Before I tear the thing open, I want to get my ducks in a row as far as diagnostic steps. Realistically, it looks like it could be one of the following:

- Binding blend door
- Blend door actuator
- Rear hvac control module

Binding would be easy to determine. But what I don't know is how to differentiate between an actuator issue or control module issue. I can't seem to find a pinout diagram / diagnostic info for this from my sources. Does anyone have info on this?

 

[tRidiot]

Blend doors... the bane of our GMT800 existence.

 

[SnowDrifter]

Ok so I was working too hard

I didn't realize that GM used the same actuator for everything. Swapped the blend door and vent control units. Problem followed the actuator

Replaced it, and she works. Honestly I'm glad it was the actuator and not the control module since said controllers are quite difficult to find

What I don't know, is there this damn piece of sound deadening(?) goes!!! It just... fell out when I was removing panels and there's not really an obvious spot I see it should go. Looks like it's been floating around in there for a while. I know I could put it back together without. But ya know what? It would drive me nuts if I do.

 

[SnowDrifter]

I will literally paypal whoever can tell me where this goes, 5 bucks.

This is beyond ******* me off. I CANNOT FIND ANYWHERE IT FITS

 

[exp500]

Location is in the assembly manual. Sorry, I don't have one for you. Upfitter may be helpful as well as parts manual.