OK, so, I searched, and while there've been threads about the AC and fans and stuff, I haven't seen this particular problem...so I figured I'd see if anyone else has experienced it:

Bout a week ago we had some nice weather, upper 60s, sunny, etc. So I decided it wasn't quite warm enough for the AC but just a touch warm to JUST have the windows down, plus I had to drive through a construction zone, so I had to put my windows up so I didn't get all that dust/dirt in the car. So I decided to kick on the vent. Turned the temp knob allllll the way over on the cold side, vent kicks in with HOT air. WTF. Now, granted, I wasn't expecting anything spectacular, afterall AC would have been way too cold, but the outside temp was just right and I wanted some more air in the car. I know the vent is always going to be a LITTLE warmer than outside, but this was HOT HOT HOT. WAAAAAAAAAAAAY too hot for vent, it felt like the heat was on.

Has anyone else had this problem??? I'm out of warranty and low on funds. I've tried turning it on on several other occasions with the same result. Even tried turning it on when the motor was still not up to temp to see if maybe the reason it was like that was the engine was realllllly warm and therefore the air in the vent system got warmer than usual. But no dice, STILL blew hot air.

 

maybe its an actuator from underneath the dash.....it controls movement from hot to cold.

 

Maybe, I've got the infamous fan squeal too. It's like the car waited until the warranty was up and then just EVERYTHING decides it needs to start making noise or not work properly...

 

the squeal could be from the blower motor, the HVAC actuator next to the blower motor cycles the temps

 

Could be, it's quite baffling. If I put it on full-blown AC then the temp is just fine, it still gets super cold. The only problem with it is on vent.

 

GM's are always hot on vent! You have to remember your venting air in from the engine bay! Mine does the same and it's nothing out of the ordinary. I had a Jimmy that could melt your feet on vent!

 

WEIRD. This is the first GM car I've had that's done this. I had a Cavalier before the Cobalt and a Skyhawk before that, none of my parents' cars ever had this issue either. Even the SS/SC has NEVER done this. This is going on the 3rd summer I've owned her (will be 2 years in June....so I had it for summer 05 06 and now 07) and the vent has ALWAYS been comfortable (except of course when it's rediculously hot out), hence why I believe it to be a mechanical problem. Also found it weird that the vent is hot regardless of the car temp (unless of course it's been off for a while and sitting in the cold) but the vent blows hot air WAY before the coolant is up to temp.

 

I always thought when you turned the temp to cold it stopped the coolant flow from entering the heater core.
If your getting heat on vent and temp set to cold the heater core has to have full flow.
I am going to look into that myself.

 

I get the mildew smell after it rains and after using the A/C...but no water on the inside...anyone have this?

 

My Z24 did this. Literally, LITERALLY, 3 miles after my warranty expired. I was sitting in my car ideling, taking note of the mileage and realizing that my extended warranty had JUST expired not 5 minutes earlier, and what happens? My odometer started blinking, and did until the day I traded her in.

Point being... I feel your pain.

 

If you complain about this the dealer will spray some fungiside in your heater core and I think they install a secondary fan that runs after you shut the car off to dry the moisture
up.
Sorry its not a tsb but a dealer information type thing ,they should take care of it under warranty.