I dunno what kinda truck you have but the AD fresh air heater fan motor in 12 volt guise is available from Grainger Inc. - I found the P/N in an old post and bought one for cheap .
Conversely the dropping resistors for the three speed fans on GM products on the 60's were always
mounted in the defroster duct so there'd be some airflow any time the motor was run .
Better fix this PDQ ~ winter is about here and SWMBO must be appeased ! .
