Question about 2002 Pontiac Grand Prix

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2005 Grand Prix heater blower does not run

I had water leaking down onto the blower and probably also the heater control module which mounts close to the firewall
, behind the blower motor.Now the blower does not run at all, but I did test it by running 12 volts to it directly. The module has 5 wires running into it's plug. I am not able to get any voltage readings at that connector, and it seems I should be getting 12 volts when the fan is set is set to run. I can't find any fuses or circuit breakers. Anyone got any ideas?

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  • vetteman_72 Dec 28, 2008

    I checked for the daytime running lights, they're lit, the LED below the heater fan speed control works until I remove the HVAC fuse in the passenger side fuse panel, and then it goes out. I have no rotation of the fan, and apparently no voltage on any of the five wires that enter the resistor module under the dash, next to the blower.

    Any further help would be appreciated

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Hi
There are two fuses for the fan. One is probably a 20 Amp in the fuse panel in the cab and marked "Heater". or "Heater/AC" The second is under the hood may be marked Heater, Blower, or Fan and should be 30 Amp. The one in the cab supplies switched 12 volts to the fan speed switch. The one under the hood supplies the 12 volts to the relay. The relay is normally energized by the 12 volts through the 20 Amp fuse in the cab and through the switch. I think you find that the fan has the normal speeds except for missing HI with the underhood fuse removed, and will turn off with the ignition that way. There is no hazard in operating it that way but you may want to replace the resistor/relay assembly before it gets too cold. The relay is a pretty trouble free device in most cases, maybe you can find a deal on a good one at a junkyard. 

The whole idea with the relay under the hood started back in the Sixties believe it or not. There is considerable voltage drop in the wiring between the fan switch and the blower fan motor. By adding the relay under the hood right next to the motor, the voltage drop was reduced, both by the shorter wire, and by using heavier wire to boot. The motor gets really close to the full system voltage when the relay is closed. In your case where the relay keeps the fan running, it can drain a battery rather quickly too!

Posted on Dec 28, 2008

  • ABHISHEK.C
    ABHISHEK.C Dec 28, 2008

    I believe you have one of two problems either your heater core is plugged up and not allowing enough flow or the temperature blend door located under the dash is not moving.The heater core is easy to check,A quick check of the heater core is with the engine running and with the blower motor off or on low carefully chck to see if both heater hoses are equally hot if not remove them from the heater core and use a garden hose to backflush it the blend door can be more of a hassle as it can be operated by a motor or vacuum servo and even a simple cable these also have been known to break but with the blower on high change the temp control from cold to hot and see if you can hear a change in the sound of the blower and sometimes you can hear the door shut it more than likely the door is ok but you will need to check it and see.
    Good Luck



  • ABHISHEK.C
    ABHISHEK.C Dec 28, 2008

    If you have a bad or leaky freeze plug, also known as soft plugs, it needs to be replaced. Your brass plugs are the best, and in some hard to get to places there are rubber plugs that can be adjusted to fix the problem. But if you have oil in the oil pan, assuming no one put water in the engine. You probably overheated the engine enough to acquire a cracked head gasket. Normaly that's the problem, could be a cracked head also, but more than likely a gasket. If you decide to remove the heads and replace the gaskets, good idea to have the heads resurfaced. (recommended) 


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Hello vetteman_72

There aren't any fuses there, there is a resistor though near the blower which probably is done and needs to be replaced for about $20 for a new one. See if you can find it, it should look like a multiple of coils.

bestdarngood

Posted on Dec 28, 2008

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Look at the dic/hvac fuze behind the glove box cover. If it has less the 12 volts on the fuze with the heater blower motor in a middle position and the head light switch off, with engine running it is probably the ignition switch. If the heater blower runs set to max (5), the blower motor is good. If the blower fails to run on some settings other than 5 but runs on others, and you have 12 volts or better on the dic/hvac fuze, it is probably the resistor pack, located behind the blower motor above the floor on the passenger side. If you pull the blower motor, oil the bearings, and check the drain hole is open (engine side). The dic/hvac 20 amp fuze is shared by many circuits, the day time run lights, seat heaters, rear window defogger, and the fancy style heater accessories, depending on the exact year of the car. All these are fed by the 60 amp ignition 2 fuze in the engine fuze block, then through the 20 amp dic/hvac fuze with the key switch in between. The DLR is located above the parking brake peddle but not much appears to go wrong with that but less than 12 volts feeding the DLR will not trigger the day time lights. Mitchell has a complete wiring diagram I got from the web for around 12 bucks, an actually has all the circuits in the set, something like 50 pages of complex diagrams! I found them here: http://www.ahdol.com The diagrams in the usual manuals from Checkers are worthless, as is who ever designed the heater resistor pack placement at GM for the Grand Prix. Hope this helps

Posted on Dec 28, 2008

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Water in floorboards 2005 Pontiac Grand Prix


We have the SAME problem. Where it is coming from is PONtiacs great job of engineering
If you remove the Plastic cowel Trim piece that is at the Bottom of the Winshield. from to do this lift the hood and take off the black platic part that is sealed against the windshield from outside. You will see that water runs down the windshield, under this trim part and drops DIRECTLY into the OPEN top of the fan/heater box. the only protection is a Cabin air filter that looks like a flat air clearner.
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