We have a 2004 Chevy Suburban. The heater blows cold air when it sits at idle speed. Any suggestions on what we can check to get this working right?

Thanks!

 

No heat just at idle? Rear heater OK?

 

check coolant level...

are you saying at idle no heat, under load heat???

check coolant level, consider a new waterpump if full.

now if your getting little to no heat and it's full of coolant, and you feel good pressure in the radiator hoses, check heater core.


:chug:

 

I would suspect possible blocked or clogged heater core...

 

Hi folks. Time for a NEW entry into the Suburban heater blows cold air subject. I have a 2009 Suburban. It's just starting to get cold in Minnesota, and I noticed I am blowing room temp air out the defroster, panel, and floor, well after engine warm-up. The manual temp control on the panel is set to full hot. The rear air gets a little warmer, and the passenger side, front, seems to blow colder than room temp compared with the driver side.

Under the hood, there are two hoses that run from and to the firewall, to the heater core. The hose closest to the fender is quite hot, and the hose right next door to it is quite a bit cooler. Obviously, the return water is colder than the supply hot water. So there must be either a blockage, or control valve stuck part way open. Is there such a valve on a 2009 Suburban in-line with the hot water supply? I couldn't find one. I suppose the core could be clogged, too. Is there a screen at the inlet?

Seems like multiple symptoms, though, because the passenger side temp is cooler than the driver side, even though the temp controls are set full hot. Maybe an air-blend door motor broken?

Anyone have experience with this?