[Mike Sz]

I have a 2002 GMC Sierra and I am experiencing less than normal heat output and sometimes very little heat. Initially I had to have the intake seals replaced and it was after that that I started having heating issues. Prior to that the heat was working fine. After the intake work was done I had no heat. At that point my mechanic replaced the heater core. At this time the intake and outtake of the heater core hoses are both hot. At this point I don’t understand what the problem is. If my heater core is getting heat then why don’t I have a good amount of heat and why isn’t my blower blowing as hard as it did before.I’m looking for any other possible issues that would be causing this. Appreciate any help.

 

[xPosTech]

Sometimes the HVAC gets confused and forgets the positions of the doors controlling the mix of hot and cold air. Google Resync GM HVAC Actuators. Sometimes it takes several different attempts to get them resynced.

Ted

 

[j cat]

sorry you had to pay a huge amount for this heater low heat type issue... not a cheap repair to replace a heater core because you get little heat.
both hoses hot good flow

the heater core has hot coolant flowing all the time thru the core..
there is at the tranny hump mounted on the heater/venting box a stepper motor. these have a 5 volt power to move the door temp .. if this gets stuck then no heat or erratic heat control.

as time passes the soft plastic does distort due to the hot air,,,,, this in my 2000 , caused the temp door stepper motor to bind up sometimes .. so I removed the motor and used two small washers to mount the motor out from the vent housing a very small amount .. this fixed the problem ..

 

[Mike Sz]

To xPosTech , after checking my particular truck doesn’t have an actuator. But I appreciate the thought. To j cat, I appreciate your thoughts and will look for this in my particular vehicle. I approach my mechanic earlier today and he seems stopped and would like to have a back and look at it. I would really like to get this figured out on my own. I have to do some more research on how the whole heating and cooling thing works. If anybody else has any other ideas I would sure appreciate them. Thanks.

 

[xPosTech]

Ted

 

[j cat]

these ON your truck should have air filters .. some have had debris even lizards [texas] get into the air box and mess up the temp door operation...

SINCE THIS WAS ALL OPENED UP NOT THE CAUSE ..

 

[Mike Sz]

OK I took it to my mechanic and he found that the air conditioning was running the whole time I’m trying to generate heat. He Disengaged The AC by pulling the AC module or the fuse not sure. He also noticed that when You chose defrost or other settings you couldn’t change it from recirculate the outside air or vice versa. Finally got it to start generating heat and thought the AC may have been part of the problem. Also was considering that the climate control itself is bad. Next day on a cold winters morning when I got up I fired up the truck and the heat and by the time I cleared off three vehicles I should’ve had some heat and I had none. Where do I go from here, thanks.

 

[j cat]

sorry not any help . you are not up to it. go to another shop that does ac work .
as I stated before the temp door stepper motor ?

in defrost mode ac compressor is on .

 

[Mike Sz]

My guy did check the actuators and they all seem to be performing as expected. I was not aware that the compressor runs when you’re in defrost mode. Thanks

 

[j cat]

My guy did check the actuators and they all seem to be performing as expected. I was not aware that the compressor runs when you’re in defrost mode. Thanks

find another guy . both hoses hot and the temp door stepper motor is working , then need an expert on this HVAC repair.