92 gmc suburban heater issues

[rogerntara]

my wifes suburban is acting weird. the heater gets cold when we come to a stop, but it gets hot once we start moving again. i just changed the thermostat. its really weird. anyone have any ideas let me know. thank you. It is freezing here in the pacific northwest and would like tio get it fixed as soon as possible. thank you again.

 

[ezdaar]

Stupid question, but is there air blowing out the vent when you at a stop?
I ask because, I am thinking maybe the blower motor is out.
If it is working, how hard is it blowing?

Do you have the HVAC on recycle or external air when your running the heater?


Other than that, sounds like you have some heavy blockage in the heater core, not allowing coolant to flow efficiently at idle, but under part throttle its enough to keep heater core hot.


Give alil more detail please..

 

[rogerntara]

It blows the same either way. The temperature just goes from hot to cold. The hvac is on recycle.

 

[bowtiefreak]

Check for a blockage like stated above. I have never heard of this before.

 

[chauncey0337]

I had a similar problem, my heat was lukewarm and wouldn't get hot. It was a heater core all gunked up. Bought a reverse flush kit from o'reilly's and some radiator Super Flush and now blows hot.