Cold air blowing when heat is on?

[whitestingray81]

Just tried to use the heater in my Avalanche for the first time, and it only blows cold air. I drove around for a while; still only cold air. I put the temperature set to 90 degrees; still cold air. I have the electronic 2-zone unit in my AV.... Here's the even more weird thing. When I turn the temp up to 90 degrees and push the "AUTO" button, the A/C button illuminates and the blower goes to feet only!

Anybody have any ideas what's going on? The head unit, probably.....

 

[whitestingray81]

Did some further testing. After several minutes it will begin to blow warm air, but not scolding hot like I expect. If I turn it to recirculating air, it blows cold again. The lower radiator hose is cool to the touch. Stuck open thermostat? My temp gauge goes to 210 degrees and stays there, so the engine isn't running too cool or overheating. Partially stuck open thermostat maybe?

 

[zora]

On a fully warmed up engine the lower hose should not be cold. You say first time you are using heat, is this a new or used vehicle? If a newer vehicle it has to be connected to a diagnostic tool to determine the cause of the issue if not a stuck open thermostat.

 

[whitestingray81]

Yes, the '07 Avalanche is new to me this past spring, so the first time I used the heat was today.

However, I FIXED IT! One of the heater core hoses was being crimped shut by the engine cover. I freed it and IMMEDIATELY got scolding hot air out of the vents, so it's all taken care of. Thanks for the response!