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2005 Sierra HVAC stuck in cold mode


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My 2005 Sierra's HVAC is stuck in the cold mode. As another Alaska winter is approaching I'd sure like to have it fixed before it arrives. I have gone as far as I could with all that I've been able to gather so far on you tube and it still doesn't work. AC works fine I just can't get it to put out heat. I have changed all the mode door actuators (even the almost impossible to get to one  where almost the entire dashboard has to be removed) except for the air recirc one which I verified works by cycling it. The mode selector was also changed and was verified to work with the proper selection of defrost, foot air, upper air etc. I changed the control panel (the one with the two knobs on either side with the vertical temperature slide levers in between) with a used one I got from ebay. I am not able to test the used unit that I bought but I would think that both control panels wouldn't have the same failure unless that is a common issue with these units. I did the pull-the-fuse re-calibration of the system as explained on you tube. I even had the cooling system flushed and the heater core back-flushed just in case there was blockage. The system was pretty much clean, still no heat. not even a little. Is there a magic control box somewhere that I may have missed? Where to next?

 

Cold in Alaska

Bob

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no sure what the cause of your issue is.  You can try a few things. 1) make sure both hoses going into your hvac and out are hot.  If one is hot and the other is not, your heater core is plugged.  2) make sure your blend door actuator is working properly.  

 

You can try to unplug the fuse for your AC and see if your truck heats up then. Also make sure your truck gets up to temp, and that you dont have a stuck open thermostat. 

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I can't figure out how to reply to individual posts in this forum. For SHARPZ as I have noted in my original post, I have tried all of what you have suggested to no avail. The Thermostat was changed a short time ago and the temp gauge shows normal operation.

For PopeyeD, I have not considered that option. Where specifically is the cabin air temperature sensor aspirator located. You mentioned over the driver's seat is it under the headliner? or behind some plastic panel that I need to remove? I have a single cab model if that makes any difference.

Bob

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4 hours ago, Robert Picard said:

I can't figure out how to reply to individual posts in this forum. For SHARPZ as I have noted in my original post, I have tried all of what you have suggested to no avail. The Thermostat was changed a short time ago and the temp gauge shows normal operation.

For PopeyeD, I have not considered that option. Where specifically is the cabin air temperature sensor aspirator located. You mentioned over the driver's seat is it under the headliner? or behind some plastic panel that I need to remove? I have a single cab model if that makes any difference.

Bob

 

To reply to a specific post, just click on "Quote", then give your reply

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On 8/17/2021 at 4:07 PM, Robert Picard said:

My 2005 Sierra's HVAC is stuck in the cold mode. As another Alaska winter is approaching I'd sure like to have it fixed before it arrives. I have gone as far as I could with all that I've been able to gather so far on you tube and it still doesn't work. AC works fine I just can't get it to put out heat. I have changed all the mode door actuators (even the almost impossible to get to one  where almost the entire dashboard has to be removed) except for the air recirc one which I verified works by cycling it. The mode selector was also changed and was verified to work with the proper selection of defrost, foot air, upper air etc. I changed the control panel (the one with the two knobs on either side with the vertical temperature slide levers in between) with a used one I got from ebay. I am not able to test the used unit that I bought but I would think that both control panels wouldn't have the same failure unless that is a common issue with these units. I did the pull-the-fuse re-calibration of the system as explained on you tube. I even had the cooling system flushed and the heater core back-flushed just in case there was blockage. The system was pretty much clean, still no heat. not even a little. Is there a magic control box somewhere that I may have missed? Where to next?

 

Cold in Alaska

Bob

I had the same issue 2005 silverado 5.3 Z71. It ended up being my blend door actuator, the easiest one to get to just under the plenum at center of dash, got lucky, recalibrated and all is good to go.  Maybe your blend door actuator is faulty that you installed.

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9 hours ago, Adamog45 said:

I had the same issue 2005 silverado 5.3 Z71. It ended up being my blend door actuator, the easiest one to get to just under the plenum at center of dash, got lucky, recalibrated and all is good to go.  Maybe your blend door actuator is faulty that you installed.

Was your problem full cold for everything including driver and passenger side and defroster? I tried two different actuators and even turned the door with my fingers and it was still nothing but cold air.

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