I've had the car for 2 years now (Wow, it doesn't seem like that long at all) and it's always done this. I've finally gotten tired of it smelling like crap whenever the heater is on.

When the slider is on cool, everything smells fine. The instant you slide it to hot the air coming out of any vent kind of smells like mold. Is there is a filter or something that needs to be changed?

 

TTt

 

No filter at all. Might want to pull the dash out so you can gain access to the heater box and core so you can pull the core and see what's going on in there. First guess would be that the screens on the A/C evaporator are clogged with mold and crap, but the problem isn't on the cold side of the system (and yes, the air first flows through the A/C evaporator, even when going to be routed through the heater core, to dry the air first). Could be something got into the heater box (mouse) and made itself a cozy nest, which is now moldy.

 

a leaky heater core will smell like death warmed over if the coolant is old and burnt.

 

I'm thinking that it probably is the heater core. I'm going to tear the dash apart soon and take a look at it because I'm tired of this.

 

its for sure the heater core... your windows probably fog up when you first turn the defroster it on as well