1997 grand prix..heater motor starts on its own at nite

[harry1877]

1997 pontiac grand prix..heater motor will run at nite after the car is shut off...runs till the battery is dead...heater motor just starts up onits own what is up.....

[BNaylor]

Originally Posted by harry1877

1997 pontiac grand prix..heater motor will run at nite after the car is shut off...runs till the battery is dead...heater motor just starts up onits own what is up.....

Do you have manual HVAC or digital climate control system?

Is it running at a certain speed?

Sounds like you may have a flaky contact in the ignition switch not opening but maintaining contact when the key is off.









Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[richtazz]

maybe the car is cold, get it a heated garage, you big meanie! Seriously though, I agree with Bnaylor, sounds like an ignition switch going bad. It could be a shorted resistor, but it only gets power when the ignition is on.

[BNaylor]

Originally Posted by richtazz

maybe the car is cold, get it a heated garage, you big meanie! Seriously though, I agree with Bnaylor, sounds like an ignition switch going bad. It could be a shorted resistor, but it only gets power when the ignition is on.

lol. Either that or he's got a Gremlin he needs to hunt down and kill.











Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[mtongen]

Originally Posted by harry1877

1997 pontiac grand prix..heater motor will run at nite after the car is shut off...runs till the battery is dead...heater motor just starts up onits own what is up.....

I had the same thing happen to my 97 GP GT. It is more than likely that it is the "Blower Motor Resistor" the ignition diagnosis can happen but not as likely as the resistor. You can find them on the internet at http://www.gmpartsdirect.com.

Here is the part# for the Blower motor resistor it's about $20. It's a son of a gun to replace but massively cheaper that taking it to a garage.

GM PART # 89018643

[regalfriend]

A side question....i hear about these cars having rundown protection...How does it work?

[BNaylor]

Originally Posted by regalfriend

A side question....i hear about these cars having rundown protection...How does it work?

It's called Battery Rundown Protection. The accessories such as interior lights, exterior lights, etc. draws a lot of parasitic load on the battery if left on. The body control module (BCM) in conjunction with the retained accessory power relay (RAP) turns off lighting and accessories after 10 minutes so the battery does not drain.

Also the BCM goes into sleep mode to minimize current draw or parasitic load. Normally, if there is more than 25mA of current draw, it will kill the battery overnight. But it depends on the reserve capacity of the battery. If reserve is 120 divide by 4 = 30mA. Parasitic load should not be over 30mA.








Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.