1997 GMC Jimmy Can't control fan speed after been operating

HIGHWAYS

MEMBER
1997 GMC JIMMY
6 CYL
4WD
AUTOMATIC
100,000 MILES

After running my fan for a hour or so, when I turn the fan speed down it works at that setting, but when I return the fan speed to maximum I have nothing. For me to control the inside temperature I have to dial down the manual temperature rather than reduce the fan speed. I have had the fan motor replaced twice with no luck.

5 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Fing the resistor and test it, it's on the a/c heater box near the fan.
ELECTRICAL TROUBLE SHOOTING BLOWER MOTOR WILL NOT RUN Check fuses. Turn ignition switch to RUN position. Check for voltage at function control switch. Switch blower switch to HI position. Check for voltage at switch and at high-speed blower relay. Ground blower motor with ignition switch in RUN position. If blower operates, motor is okay. BLOWER DOES NOT OPERATE IN HI Check for voltage at high-speed blower relay with ignition switch in RUN position and blower switch in HI position. If voltage is not present, check for voltage at blower switch. BLOWER OPERATES ONLY IN HI Check blower resistors for open condition. Check blower switch for voltage at each position. Resistor is at right rear of engine compartment on blower module.