HVAC - Driver's side only has heat

[freddyboy61]

Working on my daughter's 2003 Envoy SLT with the Auto HVAC. Driver's side only produces heat out of the vents. Bought a left side temp actuator and proceeded to remove old one (not as easy as I thought). Got it out and went to verify it not working. To my surprise, the shaft drive moved but it only cycled thru its rotation once and stopped at one of the end stops. tried the new actuator and it did the same. The setting of the temp control has no effect on the actuator, it remains at the end stop.
Is it possible that the feedback signal back to the HVAC control module is not being seen? Any thoughts would be appreciated, I have the dash partially apart and am stuck right now.

 

[Mooseman]

Did you reset the system by pulling the HVAC-B fuse? This will make the system relearn the actuators' range. Make sure you do this ONLY with the a tuators installed.

 

[freddyboy61]

Yes, the recal was done a couple of times. After doing some more troubleshooting, I believe the control panel is not seeing the feedback signal from the actuator and sends it to the endstop each time. The feedback signal is good and getting to the panel connector. I am ordering a used panel from Ebay.

Thanks for your response Mooseman.

 

[linneje]

I am not sure about this actuator, but with my rear one I had to do a manual calibration. When I put in my new actuator, despite recalibration (fuse pull) it would work briefly then jump to a default position at an endstop.

First I had the actuator hang free and request (with the electronic controls) a postion at one extreme. The acuator hanging free turned to the position it wanted.

I carefully took the cover off my actuator, and with the center gear out manually moved the white socket to the position I needed for correct insertion, then gently replaced the center gear and cover. Of course, I knew where the pin should be for the extreme, so I had manually turned it before I reinserted the actuator on the pin.

I hope this makes some sense. The other thing is that I believe a high end scan tool can command the actuator to recalibrate or assume some sort of test, although I have not tried it myself.

 

[freddyboy61]

Well this was a learning experience, first and foremost don't operate an actuator when not installed. That had me going around in circles and cost me the purchase of a control panel.

Problem was the original temp actuator, main gear was cracked causing it to hang up at the crack. Removal and installation wasn't too bad, had to cut metal bracket to get access to actuator.

After a recalibration all functions are good.

 

[Boatman]

Well this was a learning experience, first and foremost don't operate an actuator when not installed. That had me going around in circles and cost me the purchase of a control panel.

Problem was the original temp actuator, main gear was cracked causing it to hang up at the crack. Removal and installation wasn't too bad, had to cut metal bracket to get access to actuator.

After a recalibration all functions are good.

What How did you know you needed a new control panel? What were your issues? I feel I may had made the same mistake.

 

[freddyboy61]

As I said, I did not need a new control panel. I misdiagnosed the problem by trying to operate the replacement actuator not installed and operating the temperature door.

 

[Boatman]

Oops I read that wrong, I ended up taking apart my actuator and doing the re-learn process. Now everything works great. I hate that disconnecting the battery screws up the actuators, when I was just trying to save $160 by changing out the thermostat myself, instead of paying someone $220 to do it.

 

[Mooseman]

Would have happened anyway. If the actuator died because of a reset and relearn, it would have failed eventually.

 

[Fatman]

2002 Trailblazer Ltz w/ Auto Hvac control. Just replaced my AC compressor, did the normal procedure with this job. After I started to drive noticed the driverside blowing cold and passenger hot (as well as rear). Ok, had this before, did the recal. No dice. Pulled fuse, replaced. turn the key to on and watched the passenger side actuator. It moved only 45* not 90*. no extra clicking (trying to move past this point). While the recal in progress, noticed the blower was not ramping up to high speeds, but a steady slow speed. Also noticed air flow was going through the defrost and floor. After a few minutes of just watching, I decided to go ahead and adjust the controls. Fan goes to max. Air flow can function through all modes. The only thing that it doesnt do is blow cold for the passenger and rear. Now my question is, this the symptoms of the faulty actuator or the control system?

 

[linneje]

Actuators. With your 2002 the plastic in there is pretty old and the gears probably exploded. In my 2003 when I lost an actuator (battery died and the actuators recalibrated when the battery was replaced) I took it apart and the plastic gears were shattered and showed signs of aging and brittleness. You can decide which one to start on ....

I would do the back first because the actuators are actually not that bad to get at (although you do have to remove the interior molding) and you can easily see what you are doing.

 

[Fatman]

Ok. Is there an easy way to take the actuator out (glove box)? Doesn't appear so, because of the metal support in the way. (See pic). How bad would I jeopardize the integrity of the dash if I were to cut out the piece that's in the way?

 

[Mooseman]

I remember seeing on the OS that some had cut a portion of it but not the whole thing.

 

[Fatman]

OS?

 

[Mooseman]

Old Site, TrailVoy.

 

[Fatman]

Gotcha.
So pulled the actuator, opened it and low and behold the main gear to the damper was cracked. Adjusted the damper to the cold side and kept the actuator off. Got new one on order. Thanks for the help guys!