I have a 2006 SS 2.4 na. Often, when I turn the defroster on, it will fog up the windshield. And there is a musty smell. I was wondering if anybody had this problem. And does anyone know where the drain(s) for the HVAC plenum is?

 

had this problem with other GM vehicles.... mold does occasionaly grow in your ducts. You can buy a spray that you spray into your cowl while the blower motor is on to help deodorize and kill any contaminants. As for the fogging... do you have the air on recirc? that often causes windows to fog faster as the moist air inside the car is getting reused. If not then i'm not sure... maybe moisture is getting into your heating ducts somewhere.

 

Evap drain is behind the engine on the pass side firewall. Buy some evaporator anti-fungal cleaner (don't get the cheap stuff) and spray it up the drain...NAPA carries it. Fogging up when the defroster is first on is normal...the air is still cold and the a/c hasn't had time to dry the air out yet.

 

No, I don't have the recirc on. I had a problem with my Saab 9000 similar to this until I cleaned out the drain for the plenum where the heater core and cooling coil sat. There was an actual drain with a flapper type valve on it. I don't see anything obvious on the Cobalt, but then again, I don't have a lift and cannot easily see...

 

Mold smell is from your evaporator...defrost turns the a/c compressor on.

 

Thanks, now I'll know where to look...

 

You might want to check the cabin air filter if your getting some bad smell's . Ive seen some nasty **** on those .