Hey guys: Ford fan, new to this forum. Have an '09 Expedition I just got, 65k on it. First time I used heater - getting strong exhaust-like fumes, kind of like a combination of exhaust and that smell you get when you turn on an electric heater that's been collecting dust. Making me ill. This is definitely not a typical core leak - no antifreeze smell, which I know well, nor any coolant on the ground. When the a/c is on no odor at all. Does the fan take external air from different places? How could exhaust - or any engine smell - get into the heater core box? Same smell from the back unit - which is even stranger. I don't want to change the core/s unless I now it will likely fix it. This s**t makes me crazy. Any feedback would be appreciated.

 

Maybe check your cabin air filter, if equipped? if that is plugged or really dirty, you might get some odd smells. The other smell like an electric heater is maybe the fact that the blower motor, or blower motor resister pack is on its way out. Is the blower motor noisy? Does the engine have an exhaust leak? If not then it must be a coincidence that it smells like that.