2000 Grand Prix Heater blower

[bocoogto]

The heater blower on my 2000 Grand Prix malfunctions intermittently. First, it wouldn't run at any speed but high. Now, sometimes it keeps running when I shut the car off and remove the ignition key. I've read many posts with similar symptoms, but not quite like mine.

Should I start by looking at the ignition switch or heater blower motor relay?

[GTP Dad]

Change the blower motor resistor. It is located next to the fan so you will need to remove the fan to get to the resistor. That is why the motor will only run on five and sometimes won't shut off.

[bocoogto]

Thanks for the quick reply. I'm puzzled about how the blower can run with the ignition shut off due to a bad blower motor resistor. Is there always 12 volts on the circuit?

[BNaylor]

Originally Posted by bocoogto

Is there always 12 volts on the circuit?

Excellent deduction! The BMR has a high speed blower motor relay which is used for fan position 5 only. On one side of the contacts is a constant 12 volts directly from the battery. Described as "hot at all times". When you go to position 5 the relay energizes and de-energizes in the other positions 1-4. What happens is the hi-speed relay goes bad and stays stuck where the contacts pass the 12 volts directly to the blower motor and the blower stays on even with ignition to off draining the battery.