Blend Door

[Vicompc]

I have searched all the threads in relation to the blend door operation and don't see anything that points to what I have happening. The air flow on the passenger side is higher than it is on the drivers side no matter the fan speed. The actuators are moving the doors from the dash to floor to defrost, you can put the AC on reciculate and the system will see that also. Is this a problem with the actuator or is it the drivers side temp sensor?

 

[The_Roadie]

I thought the airflow was symmetrical and there's only one door, so perhaps you have some internal blockage in the plenum. Might have to drill some holes and use a borescope to see inside. The temp actuator does divert airflow from the heater core to the AC evaporator, and I have read of debris and mold build-up on the AC path. But it's not a problem that's been discussed much in the forums since I've been reading them (which seems to be a long time and a few hundred thousand posts...)

 

[Vicompc]

Thanks I'll get in there and look, I would assume the blockage would be somewhere from the blend door to the vent so at least the search area would be limited.

 

[Vicompc]

First, Roadie thanks for all the help sometimes I really think I'm the village idiot when it comes to this truck. I checked the system and found no blockage but the blend door on the drivers side was partially shut which looks like it was causing the problem. I found the following reset proceedure and it worked, the AC now blows the same on the passenger and drivers sides.

1. Adjust the passenger side to full hot and the drivers side to full cold and put the system in AUTO mode.
2. Turn off the ignition and turn it back on. In AUTO mode you will see the fan speed automatically adjusting up and down.
3. Reverse the settings, drivers full hot (90 degrees) and the passenger full cold (60 degrees). Put it in AUTO mode and turn off the ignition and then back on.

While doing this I almost had a heart attack thinking I had caused the actuator to fail (it started blowing HOT), but it reset in about 2 minutes to cold.

 

[The_Roadie]

Amazing. I never ever heard about that procedure or read it in the service manual (which I read cover to cover during the month after I bought it). I see it mentioned in full size truck forums, but never for the GMT360. You have definitely discovered something new. Thanks!

 

[mrrsm]

This is quite an Old Thread ... but occasionally on rare issues involving Body (BXXXX) Codes B0159 and B3761 or mentioning Repairing Blend Door Actuators with precise insights, information like THIS data culled into a PDF is worth saving for our HVAC SMEs ...especially for those with Tech 2s and other High End Scan Tools:

Sparky's Answers - 2002 Chevrolet Trailblazer-Air Will Not Blow Out Of The Floor Vents For Heat

Rodney: My HVAC blows hot and cold but all vents are open except driver and passenger feet vents. I bought a mode actuator but that didn’t solve the problem. I recalibrated the hvac many times via snap on scan tool. Pressing the mode button doesn’t change the vents direction. I have two codes...

sparkys-answers.com