Pontiac Grand Prix heater problem

phrozen87

I recently bought a 2000 grand prix se. The heater would only work on high (im guessing blower motor resistor. My dad was driving it down the interstate after work the other day with the heater on when all of a sudden smoke blew out through the vents and the blower motor stopped working completely. It no longer pushes air. I ran cables straight from the battery to the blower motor and it spins fine like that plus I also went down and bought a new blower motor ($75), hooked it up and still nothing. I bought a heavy duty circuit tester and im gonna try to probe the pigtail for the blower motor, and im also going to try to probe the motor blower resistor plug. Is their anything else i can try to attempt to figure out what the problem can be? Does anyone have any other ideas of what it could be? I wasnt in the car at the time so i cant really say if it smelt anything like anti freeze. Any help would be appreciated as it is starting to get bad out with the cold rolling in. Plus driving to work at 4 am with the windows fogging up is not the best thing to be doing. thanks ahead of time.

imidazol97

phrozen87 said:

I recently bought a 2000 grand prix se. The heater would only work on high (im guessing blower motor resistor. My dad was driving it down the interstate after work the other day with the heater on when all of a sudden smoke blew out through the vents and the blower motor stopped working completely. It no longer pushes air. I ran cables straight from the battery to the blower motor and it spins fine like that plus I also went down and bought a new blower motor ($75), hooked it up and still nothing. I bought a heavy duty circuit tester and im gonna try to probe the pigtail for the blower motor, and im also going to try to probe the motor blower resistor plug. Is their anything else i can try to attempt to figure out what the problem can be? Does anyone have any other ideas of what it could be?

The system is likely wired the way a manual speed leSabre was. There is a direct circuit to the blower motor for high speed with full power. There's a 30 amp fuse in that circuit.

The lower speeds were fused through a 15 amp fuse and the system switches between the two power lines using a relay that connects the lower powered speeds through the switch on the dash and then when that switch is on HIGH the relay switched to the other contact which is the 30 amp line.

I suspect your blower motor is worn and was pulling high amperage which can burn out the wires that are the resistors to give the low speeds. Then it overheated while running on HIGH speed. Hence the smoke. That may have blown the 30 amp fuse. It's good you have a different blower motor. I would not trust the original unless I could test the amperage (was it making any noise as it turned indicating a worn bearing causing more power draw to turn it?)

I'll try to find a circuit diagram for a manual control in the Grand Prix. I may be giving completely wrong advice.

imidazol97

Here's a circuit diagram. It's pretty much as I guessed based on the leSabre.

Check both fuses.
Check for power at the blower motor connection.
Check for power at the blower relay that switches between the inside control panel
connection for the lower speeds and the 30 amp high speed line.

The other thing is sometimes the connectors can burn due to heat and
the plastic distorts which lets the contacts not quite touch. Or the contacts
burn from the heating load and don't make good contact.

The relay has contacts inside that can burn and not give a circuit
through that side. The relay cover may be removable so you can
inspect the contacts--it's not meant to be removed but you may be
able to do that.