no heat until moving?

[rgouette]

Howdy,
I've seen other folk posting very similar issue, but noone replied, hoping
for some thoughts..
2005 LS2500 Suburban that , even if up to temp doesn't blow hot air until the truck is MOVING.

Ideas?
Thanks lads,
Rich

 

[zora]

You have checked the coolant level? Nothing has been done to cooling system that would have left air in the system? Issue with your heater control valve if equipped with one, vacuum line leak? Read this general article on heating systems.

http://www.fixya.com/cars/r6235876-no_heat_fan_blowing_cold_air

 

[MORAV]

Ditto the coolant level. Even as far back as my '96 Burb, heat will not work when coolant level reaches a certain level, by design.

 

[VanGo]

The only thing 'moving' related that I can think of is RPMs increase so waterpimp spins faster. Might be compensating for low coolant level. I.e. a normal coolant level might circulate through the core easier at idle. Just a thiught.

 

[mviinc]

This indicates low coolant level. Bad air pumps or looks an Air pocket in the system. When you change the t-stat, that eradicate that opportunity.