skeeljc

I have a 2004 GMC Sierra 1500 pickup. It has the auto temperature HVAC control.

When it is raining and cool (50 degrees F) the HVAC system quits moving air. The fan runs but no air comes out of any of the outlets in any mode setting (front, feet, windshield). It works just fine when it is not raining (normal humidity of 30 to 50 percent) in both the heating and air conditioning situations.

What do I need to check or replace?

2002_Z28_Six_Speed

iTrader: (20)

The automatic climate control on this model year is a pain. The control motors for the blend doors will wear out or loose track of where they are. There is a procedure to relearn door position. Try that first. Living with this truck will mean a dance of pulling fuses and the battery to try to get the bitch to relearn.

If that doesn't work you may have to replace a motor. Two of them are at the bottom of the dash and easy to get to. The rest require dash removal. The one you are talking about will require dash removal. It isn't fun the first time but once you know how it isn't too bad.

skeeljc

So what is the "relearn" procedure?

ezdaar

iTrader: (1)

If you needing to do a relearn of the doors, replace them as they are shot.


Go full cold on both sides, turn truck off.
Turn truck on and turn to full hot, turn truck off.

Start truck and try your luck, works 50/50

stroker87

iTrader: (6)

few weeks ago i replaced the passenger side blend door actuator it really was a PITA!

i didnt remove the dash only the top cover witch can be removed in less then 15 minutes and with the use of a pry bar pushing the duck work up i was able to get enough room to get a socket and ratchet in there taking my time cussing a lot it took about 2 hours

plenty of video's on youtub on doing it the way i did