Heater blower stays on when key is off 2004 grand prix

SOURCE: 2005 Grand Prix GT

There is a heater resistor module, it is located on the passenger side under the dash by the blower motor. It is a bit tricky to get to but isnt to hard to replace. I just dealt with this issue in May. The unit cost me about 86 dollars from the dealer. But be careful becuase normally the resistor goes due to a short in another component in the syste, so this may not be the complete fix for you. My main culprit ended up being the blower motor.

Good Luck

SOURCE: 2004 Grand Prix blower

assuming you know where your blower motor is you can check the motor for power with the switch on and see if you have battery voltage at the connector. if you do then it is a bad blower motor. Most of the time when a resistor goes out it will work on high only but no other settings. with it not working at all seems to be motor. Hope this is helpful.

SOURCE: 2001 Grand Prix: can't find the blower motor resistor on 2001 Grand...

Under the passenger side of the dashboard is a carpeted cover you'll need to remove. Once that's out of the way you'll see the blower motor on the RH side and just to the left of it right next to the frontwall is the blower motor resistor held in by two screws.
Here's a picture of the old design (right) versus the new design (left).

Duane Wong

• 6826 Answers
• Posted on Nov 19, 2010

SOURCE: 2006 grand prix heater only blows cold air. both

Sounds like the temperature blend door actuator may be bad or the vacuum hose to it is disconnected.

Poor Heater System Performance CAUTION
Check all fluid levels and adjust as needed, before operating vehicle for extended periods at idle.

1. Start the engine.
2. Idle the engine until the thermostat opens (upper radiator hose will be hot) Is the engine at normal operating temperature (approx. 200° F)? If yes, go to the next step. If no, go to step 16.
3. Set the mode selector to FLOOR mode.
4. Set the heater control selector to the warmest temperature setting.
5. Set the blower speed the lowest setting.
6. Carefully feel the inlet and outlet heater hoses at the heater core. Is the inlet heater hose significantly hotter than the outlet heater hose? If yes, go to step 14. If no, go to the next step.
7. Set the mode selector to PANEL mode.
8. Select the maximum blower speed.
9. Select the warmest temperature setting.
10. Place a thermometer into the center I/P PANEL air outlet and affix a second thermometer to the heater core outlet heater hose.
11. Record the temperature at the center I/P PANEL air outlet and at the heater core outlet heater hose. Are the two temperature readings about equal? If yes, go to the next step. If no, go to step 13.
12. Inspect and repair the cowl, cowl area, recirculation door, and the HVAC evaporator/heater core case for cold air leaks. Repair any problems found, go to step 17.
13. Inspect the temperature door operation. Repair any problems found, go to step 17.
14. Turn OFF the engine. Back-flush the heater core. Start the engine. Select the FLOOR mode and the lowest blower speed. Select the warmest temperature setting. Feel the temperature of the inlet and outlet heater hoses at the heater core. Is the inlet heater hose feel significantly hotter than the outlet heater hose? If yes, go to the next step. If no, go to step 17.
15. Replace the heater core. When the repair is completed, go to step 17.
16. Check for low engine temperature problems, Repair or replace as needed, go to step 17.
17. Operate the system in order to verify the repair. If the system operates properly, the repair is complete. If the heater still does not work properly, repeat the entire procedure.

SOURCE: The interior blower will not turn off even when

This is a short with a sensor called the heat sync this occurs when the weather stripping on the outside of the passenger side of the windshield gets warped and lets water in. That water builds up and blows this sensor and the blower resistor resulting in the blower relay to stay in the on position. Replacement of the resistor is needed. Replacingthe blower motor is recommended but may not be necessary depending on the condition.