Heater issues

[Debbie Lakey]

I have an 03 Sierra 1500hd and the heater is ticking me off, it’s got a brand new blower motor and resistor but for some reason it won’t blow out in of the vents,,, I’ve changed the actuators and still nothing,, is there something else I can try?? Help please running a propane heater in the truck sucks. 

[CamGTP]

Does it blow heat out of anywhere?

 

Or does it blow air out of anywhere hot or cold?

 

If it does blow air but not hot it's either the heater core isn't getting hot coolant or there is still a blender door that is not moving and switching over to heat.

[Brenden Burnham]

If it is same whether it is hot or cold then most likely your mode door actuator.  Check if you are actually getting air out just the defroster vent, even if it is a little.  And if you try and change modes and you hear nothing than that is what it is.  If so then that means it is stuck but you actually can manually move it to blow out the front vents.  The actuator is right below the steering wheel near the gas pedal and can see it.  Remove that duct that goes across off to get easier access.  You can then access it.  If you feel the top part there is a lever that moves which switches it from defrost to regular.  You can manually move it I believe up and it will change to blow out the front vents.  Give that a shot.  Can be kind of a PITA but I was able to.  I had this happen to me.  No air was coming out to find out was stuck blowing out the defrost.  I manually moved the lever and started blowing out the vents.  

Edited February 15, 2022 by Brenden Burnham

[Brenden Burnham]

Look up on YT mode door actuator and you will see what I am talking about.

[royboy09]

I'm having the same-ish issue. 2006 Sierra fan won't blow. I've replaced the resistor and the actual fan but still no go. I'm gonna try replacing the factory plug harness that goes to the resistor next to see if that helps. I saw a YT video where a guy did that and it worked for him.