Re: Dash blower fan E-350 V-10 gasser
The High speed fan is direct 12 volts and might have a relay, I could check my 2008 manual. The other three speed are the resisted ones. Usually if the resister is bad you have no 1, 2 or 3 and only high works.
As for the going up hill part that sounds like vacuum. Any chance the fan is blowing but changes from out of the dash vents to the defroster on top of the dash? On most cars and trucks with vacuum operated heater and air conditioning controls defrost is the default if it loses vacuum. If thats what is happening its most likely a check valve
2008 Ford E-350 V-10 EB
U-Joint Off Road 4x4 kit in the garage
2004 F-350 Dana 60