Heater Problem

kodyind · Sep 27, 2015

I have a 2005 Avalanche and I am having a heater problem, it seems it has a mind of its own, sometimes it will be working as it should and then it will start blowing cooler air not cold air but cooler and even if I turn up the heat it does not change and just today it was set at 72 and it was 75 out side and all of a sudden the heat came on and it kept basting hot air so does anyone have an idea what this could be

Jim

MS03 2500 · Sep 28, 2015

HI Jim check your coolant level, if it's low it will do this.

kodyind · Sep 28, 2015

I did that and it is fine

MS03 2500 · Sep 29, 2015

OK I'm a bit confused here so I'll ask a couple of questions

Is your problem the temperature or the fan speed.

I guessing you have the Auto AC with the temperature LED display.

kodyind · Sep 29, 2015

It is the temperature and yes I have the auto controls, like today i had it set on 73 and it was 74 outside and after about 20 mins all of a sudden the heat started blowing out like i had turned it up to 85

MS03 2500 · Sep 29, 2015

You did not happen to open a window before it started acting up.

You can try resetting the HVAC controls.

Turn the system off first
Pull the fuse labelled HVAC in the under hood fuse box wait 2 minutes and put it back in.

kodyind · Oct 1, 2015

Ok I pulled the fuse, waited 2 mins and now it I cant get it out of defrost, the controls show it is on vent or the lower setting but it does not disengage from defrost

MS03 2500 · Oct 1, 2015

Did you turn it off first.

kodyind · Oct 6, 2015

yes I did

dogmus · Oct 25, 2015

There was a recall for this a few years back. Sorry I don't have the recall number handy. The issue was moisture getting into the blower motor resistor and causing a minor short at the resistor wiring harness. The dealer tried to sell me a new harness for my 06 Z71 for about $100.00. I found it online for $19.00 plus shipping and installed myself. Don't know why but my VIN was not covered under the recall even though I had the exact problem(

).
The new harness fixed the problem for about a year and I had to install another one when the problem resurfaced in extreme cold temps. All seems ok now.