2007 impala heat question.

[crothmeier]

I have a 07 Chevrolet impala that I have a heating question on. I first noticed the issue at the end of last winter. When I have the heat on and I'm driving it works fine, blowing hot air. If it idles in park, or when I let off the gas at a stop sign it blows cold air. So when I start my car to let it warm up it just blows cold air until I start driving and increase rpm. Wondering what would be causing this and if it is related to the rear defrost not working either. I assumed the fuse was to blame for that, its a bigger square grey relay-type fuse under the hood.

On a side note the fan speed is not affected by idling or driving, it stays the same, just the temp of the air changes.

I appreciate any advice if I can fix it myself that would be ideal otherwise ill take it in.

Thanks!

[Jeremy airjer W]

one of three things.

Your t-stat is stuck open in which case your check engine light should be on.

Your coolant is low.

Your heater core is plugged.

[crothmeier]

A lady I work with has the same car, with the same problem, except her rear defrost works.

She called the dealership in town and they mentioned coolant first, but asked her if her rear windshield defrost was working because of a switch that goes bad behind the dash that controls them. I'm going to check my coolant on my lunch break.

Is this switch anything anyone has heard of?

[Jaspernuts]

One thing I have seen numerous times on this vehicle is an air pocket gets trapped in the cooling system and needs to be bled out.

[crothmeier]

The coolant is low, but I don't think low enough to cause this problem. I'm going to add more and see if it solves the heating issue. As for the rear defrost not working the fuse is good, I'm going to put a tester on the relay and then back at the rear windshield grid to check for power. I was told that the connectors back by the grid fail which must be common.

Thanks for the input airjer and jaspernuts I will report my failure or success

[BobT]

I had this problem with a 70's model citation. This was before all the electronics started getting into the picture. I replaced thermostat, flushed the cooling system, disconnected hoses and flushed the heater core by itself, and it didn't change. I finally came to the conclusion that it was because the engine was so small that it couldn't generate enough hot water flow through the heater core fast enough to keep the core hot. I doubt this your problem though.

[crothmeier]

Coolant fixed the issue. It was a half jug low. Haven't had time to dig into the rear defrost other than the fuse is good and the relay clicks when the switch is turned off and on. Looks like ill be scraping that today with this lovely freezing rain we are getting!