2005 Sierra Heater Problem

yamahadude9 · April 9, 2010

My father has a 2005 gmc sierra 1500 that he has been complain to me about and i want to fix it for him but im not exactly sure what the issue is. I'll explain what its doing, it will only blow hot air when you set temp adjustment on its hottest setting, if you turn the temp down just a hair from max it will blow cold air. So its feast or famine you either sweat your butt off or freeze. I appreciate the help and i know he will too, have a great day !

yamahadude9 · April 10, 2010

Nobody has any idea on this one ?? I know its my first post and i hate to come outta the gate with a question but this place seems like an awesome site with lots of knowledgeable people and a great place to ask. Looking forward to a response TIA

My father has a 2005 gmc sierra 1500 that he has been complain to me about and i want to fix it for him but im not exactly sure what the issue is. I'll explain what its doing, it will only blow hot air when you set temp adjustment on its hottest setting, if you turn the temp down just a hair from max it will blow cold air. So its feast or famine you either sweat your butt off or freeze. I appreciate the help and i know he will too, have a great day !

remington351 · April 10, 2010

I have not had any heater issues, but it is a frequent entry on the forum. I'm sure someone will respond with more details but in the meantime do a search for "blend door" or "blend door actuator" and I think you'll find lots of information. Here's a TSB that I found when I did a similar search. Good luck.

Subject:Repeat HVAC Actuator Replacements - keywords door cool heat mode temperature #PIT4427 - (06/15/2007)

Models:2003-2007 HUMMER H2, SUT

1999-2007 Chevrolet Silverado Classic

1999 -2007 GMC Serria Classic

2002-2006 Cadillac Escalade, ESV, EXT

2000-2006 Chevrolet Avalanche, Suburban, Tahoe

2000-2006 GMC Yukon, Yukon Denali, Yukon XL, Yukon Denali XL

2002-2007 Chevrolet Trailblazer Models

2002-2007 GMC Envoy Models

2004-2007 Buick Rainier

2005-2007 Saab 9-7X

1998-2004 Chevrolet S/T Classic Blazer and S10 Pickup

1998-2004 GMC S/T Classic Jimmy and Sonoma

1998-2007 Oldsmobile Bravada

2003-2006 Chevrolet SSR

This PI Being Updated To Add Additional Model Years. Please Discard PI02080.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

A replacement HVAC actuators is inoperative or that has worked one time and quit. The HVAC control head learns the stopping points based on how far the HVAC DOOR travels. If the actuator reachs the mechanical stops on the back of the actuator it will be outside of the range that the HVAC control head can learn. If the actuator was not mounted to the HVAC case prior to plugging in its connector, the actuator will go out of range and be inoperative.

Recommendation/Instructions:

Always attach the HVAC actuator to the case before installing the electrical connector.

If an actuator is out of range it may be possible to bring it back into range by following the procedure below:

Turn ON the ignition, with the engine OFF.
Connect a 3 amp fused jumper wire between the actuator control circuit and the 5 volt reference circuit of the actuator connector.
Remove the jumper wire and actuator connector when the actuator is at the center position.
If the actuator doesn't move in step 2. Try installing the jumper wire from control circuit and the ground circuit of the actuator.
With the actuator in the center position, install the actuator to the hvac case and secure the mounting screws and then connect the actuator connector.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.