Awful "garage" smell in the cabin won't go away

[agp22]

Hi everyone. In my 2014 328I there is a strange smell, similar to the smell of an old garage that accumulated a lot of dust. Reminds me of black dust I have seen in old garages.

If the AC is on, the smell goes away, until the AC is turned off. Then it resurfaces.

If I drive with the windows only a bit open, the smell comes on again. Even if the AC is on. If I shut the windows and leave the AC on, the smell disappears.

If I drive with the windows fully open, the smell goes away while I am driving.

If I park and leave it with the windows open, and step outside of the car, simply walking up close to the windows will allow to identify the smell.

I have changed the AC filter, and washed the thing several times. Tried the air purifying treatments. Changed the floor mats. The smell is still there.

I wonder if I have to change the headliner next.

The car sat for about 3 years with very little mileage prior to me purchasing it. I wonder if it sat for years in a garage with the windows opened.

Any ideas?
Many thanks

[jclausen]

Try heater temp on full, fresh air selection, blower on high windows down, let the car idle in the drive way for 5-10 mins. Some times mold can grow in heater box

[agp22]

Thanks, it's beginning to go away.

[Joseph.N]

Try these.

1. Make sure there’s nothing creating the smell inside the HVAC system

2. Clean everywhere in the car including taking the seats out and steam cleaning under them (usually the culprit)

3. I would check near the HVAC intake (right in front of the windshield) and see if there’s anything blocking or if there’s anything inside it.