Heater

[04yukon22]

I just bought my 04 yukon and my heater is not working when i turn it on. but, it works if i just let outside air come into the cab. what is wrong?

 

[Goldcuffs]

So you have heat when recirculate is NOT on? By no heat, do you mean blows cold or does not blow at all?

 

[NJTaho]

I would do a coolant flush and run a hose through the heater core. I had a similar problem when I got my tahoe. There was almost no coolant and the heater core was clogged with alot of gunked up dexcool. Get some cooling system cleaner and run a hose through the system until it comes out clear, and then put the cooling system cleaner in and let that run in the system for a little while. drain all of that out and then fill it back up with some fresh 50/50 Dexcool and you should be good to go.
If that doesn't work you may need a heater core.

 

[chauncey0337]

Dan, that doesn't explain why it works in fresh mode and not in recirc mode, But it's always a good idea to flush system if it hasn't been done recently.
Bobby, need more info, be specific- not blowing? not blowing hot?

 

[NJTaho]

I had the same problem with my heat when the core was clogged and it happened to be the heater core being clogged. When I would drive and have the heat off but on fresh air it would blow hot with the heat coming off the engine itself. I had the cooling system flushed at pepboys, which was a mistake and a waste of money, and ended up having to do it myself anyways. When I would put turn the heat on it felt like the AC was on. But after flushing the heater core and running the hose through it, it's HOT!

 

[chauncey0337]

Not to get off topic but are you sure air comes from engine bay when in fresh air mode? I always thought the fresh air came from the cowl below the windshield.

 

[NJTaho]

Not to get off topic but are you sure air comes from engine bay when in fresh air mode? I always thought the fresh air came from the cowl below the windshield.

Honestly I'm not sure, i'm kinda speculating here.
But if you don't have the air on at all, at 0, and in fresh air mode but the thermostat is turned all the way on max heat, then while driving warm air will come through the vents. So I'm not to sure if the air comes through the cowl below the windshield.

Also, if you have the heat on and in recirc mode, then you are only going to be recirculation cold air.

 

[chauncey0337]

Honestly I'm not sure, i'm kinda speculating here.
But if you don't have the air on at all, at 0, and in fresh air mode but the thermostat is turned all the way on max heat, then while driving warm air will come through the vents. So I'm not to sure if the air comes through the cowl below the windshield.

Also, if you have the heat on and in recirc mode, then you are only going to be recirculation cold air.

Yes, air off, fresh mode, will push out air because on our trucks even if air is off a little bit of air is still pushed out the vents. It's hot because when thermostat is on max, the blend door is turned to the heater core.