L. Ross 4/25/2011
2001 Mercury Mountaineer Base 8 Cyl 5.0L
Body & Interior
Automatic climate control fans runs only on high speed.
The automatic C/C system fan speed only operates on high. It initially seemed to short into "on mode" despite being in the "off" position (the fan wouldn't shut off). After sitting for two days in the off position, the fan finally shut off. Now the fan only comes on when turned to high.
Sounds like your blower motor resistor is already faulty.