2005 Chevrolet Tahoe – Front & Rear Heat & Air Not Working Correctly

RFulton: Need help with front and rear air for my 2005 Tahoe with dual zone automatic HVAC because it was blowing cold on driver side when temp was turned up all the way. After trying to recalibrate it finally worked, however when you change anything on diver side it gets cooler then heats back up, passenger side stays like it should. Also my rear air blows cold air only, I have replaced both of those actuators too, not sure how to calibrate the rear and a little worried that trying to calibrate rear may screw up what I have up front. It took at least a dozen times to get the front to get hot air on driver side.

Sparky: If you have manual controls for the rear HVAC system there is no recalibration procedure. If you have auto controls for the rear there is not a clear procedure but you could do a standard recalibration procedure but you would need to remove the ECC fuse from the interior fuse box to start the recalibration. This will not affect the front system.

On the front system problem it sounds like the driver’s temperature door actuator is failing. I would recommend replacing it if it gives anymore problems. A long shot temporary repair would be to remove that actuator and disassemble it. Look to see if it has brass contacts under the large gear. If it does wipe the grease off of the contacts and off of the mating surfaces on the circuit board. Some of the actuators have a potentiometer instead of the visible contacts under the large gear and not much can be done to improve the performance of those.

RFulton: The temp door actuator was brand new when I put it in today, could it be something else possibly? I really don’t want to tear into that dash again.

Sparky: Which actuator did you replace and what was the part number? The driver’s temperature door actuator is located under the passenger side of the dash above the transmission hump in the floorboard.

RFulton: I checked the front, and passenger side only puts out hot air. While driver side no matter what temperature setting, seems to cycle between cold and hot about 10 seconds each.
Man I just thought that the old vacuum operated switches were a pain now I see they were a piece of cake compared to these electronic actuators.

Sparky: There are pluses and minuses to both types of systems. The electronic systems have made extremely good automatic climate controls possible so I am more in favor of the newer style. I like setting the temperature and letting the system do it’s job.

RFulton: Any ideas of why driver side cycles 10 seconds between hot and cold, yet passenger side stays hot. Blend door actuator and temperature door actuator were replaced at same time yesterday. When it cycles cold it kicks on compressor even when it is not in defrost or the a/c button activated?

Sparky: Try disconnecting and reconnecting the harnesses at the passenger end of the dash under the trim panel at the door jamb. Treat it like a recalibration has been initiated when you turn the ignition back on.

Beyond that there is some testing that can be done with a voltmeter if you have one. It would be much better if you had the use of a scan tool that can communicate with the HVAC system.

RFulton: I replaced the temp actuator( behind passenger left dash vent) and the blend door actuator (about 4″ above the right side of transmission hump). I get hot air from passenger but not driver side. After pulling fuses HVAC ECAS and the two at drivers side of dash I can see the temp door going from about 2:00 to about 10:00 and back to 2:00 where it stays.

Sparky: What was the part number of the installed part at the right side above the transmission hump?

RFulton: I believe it was a Dorman 604-111.

Sparky: The correct Dorman part number for the driver’s temperature door actuator (the one just above the transmission hump on the passenger side)  would be 604-106, the ACDelco part number is 15-72971.

RFulton: What is the correct part for the blend door? I was under the assumption that the lower one was blend door actuator and the upper one was temperature door actuator.
The guys at Oreilly auto parts said they were the same and sent me home with two of the 604-111

Sparky: Here is the deal. I only use ACDelco parts on those repairs and I know that on your truck with auto controls that the 15-72971 is the correct actuator for the driver’s temperature door actuator, passenger side temperature door actuator and the air inlet actuator.  Going to Dorman’s website and cross referencing the 15-72971 number brings up the Dorman 604-106.

Also early on GM and ACDelco had the wrong part numbers listed for those actuator in their cataloging. The aftermarket copied that information and sometimes never got the corrected info.

RFulton: Wow, finally got correct actuators and the right parts make all the difference in the world, thank you so much.

I figured it out too late but instead of turning the switch off for the dome lights when doors are opened I disconnected the battery to do all the work. So now I have nothing but cold air in rear hvac, would you mind telling me the best way to recalibrate the rear hvac i.e. Which fuses to pull and correct order and times of procedure?

Sparky: If you have manual controls for the rear HVAC system there is no recalibration procedure. If you have auto controls (which you do) for the rear there is not a clear procedure but you could do a standard recalibration procedure but you would need to remove the ECC fuse from the interior fuse box to start the recalibration. This will not affect the front system.

RFulton: Are there specific settings for the front and rear controls when you recalibrate rear auto air? Also how long should ECC fuse stay out?

Sparky: No special settings needed. Leave the fuse out for one full minute. Reinstall fuse, turn ignition on for one minute, do not touch anything, turn ignition off for at least 10 seconds but no more than thirty. Start the engine and check the system.

RFulton: Thank you, the rear HVAC now will allow to adjust temperature.