is there a 'master' blend door that would explain this?

[George B]

Which one, right connector right at the unit, or the one on the right side of the candi twit in this pic.

View attachment 276215

Right side of the Candi

 

[Sparksalot]

Right side of the Candi

That’s the one I figured caused problems. I’m getting nowhere with it. I pushed the ever loving crap outta the thing. Just now I tried it I little loose to fully pushed in. No luck.

 

[George B]

That’s the one I figured caused problems. I’m getting nowhere with it. I pushed the ever loving crap outta the thing. Just now I tried it I little loose to fully pushed in. No luck.

Bummer. I found bits of plastic flash in the connector on mine. How long have you had it? Maybe see if you can get a replacement?

 

[swathdiver]

Which one, right connector right at the unit, or the one on the right side of the candi twit in this pic.

View attachment 276215

Mine acted up tonight too, first time ever. Had to push on the connectors and all was well. I have replaced the cable with one from Amazon too.

A system with rear AC has six actuators and three part numbers if memory serves on the GMT900s.

Mode Door - 89018374/15-73952 (in my hands)
Recirculate -
Driver's Side - 89018365/15-72971 (in my hands)
Passenger Side - 89018375/15-72972 (pretty sure)(works opposite of driver's side)

 

[Sparksalot]

Bummer. I found bits of plastic flash in the connector on mine. How long have you had it? Maybe see if you can get a replacement?

It worked fine when I got it. Then it didn’t.

a little over a month.

 

[JonnyTahoe]

Don't we have 3 blend doors? One on the driver's side, one on the passenger side, and one in the middle (the infamous one that requires dash deconstruction to reach)?

I removed all the vent tubes and other parts of the structure. This is my 2000 Tahoe with complete airbag removal. I'm parting out the truck so I took a few pics for you guys.

 

[JonnyTahoe]

The mode actuator controls where the air is sent to, windshield, bi-level, up and down, etc. If it is not right, it too can bleed off air. The mode door is accessed from the driver's footwell.

 

[JonnyTahoe]

Yes, the front and rear have their own separate systems. The rear is located behind the passenger side rear compartment. There’s a separate heater and ac unit there, with its own blend door and mode door with corresponding actuators. Up front there’s 4 actuators- blend doors for passenger and driver temp control, mode door to tell the air which vent to blow out of, and recirc door to tell the system to either draw outside air in or to recirculate the inside air. The recirc is the hard one on the NBS. I replaced mine in a couple hours by only removing the dash cover and then removing enough screws from the supporting structure that I could pry it up enough to get to it.
So in total that’s 6 actuators.

Couple hours not bad. I spent a bit more. The one video I watched the guy was able to easily remove his dash cover. mine had never been removed and they can be completely stuck near the windshield.

 

[JonnyTahoe]

can anyone comment...so what I did is pull the driver side blend door actuator, since it's relatively easy to get to. I had set the temp to 60 and the actuator was all the way to one of the hash marks, i.e. it appeared correct. More importantly, I manually twisted the blend door shaft to the extreme, and the air up on the driver side was still tepid...so there must be *something* sitting ahead of it.

@swathdiver you mentioned the mode door, can you elaborate?
or can anyone else elaborate on if there's a door that sits ahead of these 2?

bear in mind the rear air is super cold, so I don't think it could be a problem under the hood...

So this is what your talking about that is easy to get to? How were you able and with what twist the Mode Door shaft without damaging it?

 

[bmishoe]

I ended up taking it into the dealer. Their finding was "a short on the HVAC control module", and a leaking fitting on the high-pressure side. I'm not sure how that explains the symptoms I was experiencing, but they replaced the module and recharged the system and all is well. I guess time will tell...