I drive a 2004 Pontiac Grand Prix and the AC/Heater/Defrost is very tempormental. Sometimes it does work perfectly and come on just fine other times it makes a weird noise like it is trying to turn on and does not then I hit the dashboard and it does. When it is on the blower works perfectly. So is this the blower or is this the climate control unit or wiring or any other possibilities?

SOURCE: blower motor only works on high

located under dash next to blower motor itself should be a couple of wires plugged into it

SOURCE: 2005 Pontiac Gran Prix blower

Check the blower motor which is behind the right side of the dash, in the lower right side of the HVAC Assembly, above foot area of the passenger floor. The other thing to test is the blower motor resistor which should be next to the blower motor.

SOURCE: blower fan only works on high

CHECK THE HVAC CTRL FUSE.

WITH A TEST LIGHT CHECK THE BLOWER RESISTOR FOR POWER ON THE YELLOW, TAN, PURPLE, AND LIGHT BLUE WIRES. THE ORANGE WIRES CONTROL THE HIGH SPEED CIRCUIT. DO THIS FOR EACH POSITION OF THE BLOWER SWITCH.

THE BROWN WIRE ON THE HVAC CONTROL CONNECTOR 1 POSITION B COMES FROM THE HVAC FUSE 20 AMP. NO POWER ON THAT WIRE WILL CAUSE THE BLOWER TO NOT FUNCTION ON THE LOWER SPEEDS.

Steve Allison

• 5569 Answers
• Posted on Aug 21, 2009

SOURCE: Blower motor not working on 1999 Pontiac Grand Prix GT

The blowers vary greatly relative to accessibility; some are back-breakers and only removable from under the dashboard. Make sure you don't have a blown fuse or failed relay; neither of these are costly and both easy to replace. On the relays, there are often multiples of the same part number which allows for swapping to check for operation. They will have a part number that you can compare so you are sure you are putting the same part where it belongs when swapping.
> I can hear the fan kick on, but nothing else happens.
I assume you mean the cooling fan under the hood, not the AC/heater blower.
Most often, the blower will continue to function on the highest speed setting and this common problem is caused by the failure of a special stepped (tapped) resistor that is used to 'waste' some of the voltage therefore changing the speed of the blower.
I recommend that everyone have a cheap multimeter at home since these are now under $20 US and let any layman do some electrical checking without paying an expert. Such a meter can be had at Radio Shack or any auto parts store and are easy to use. Having one of these, you can often ferret out problems such as yours quite quickly and they are handy around any home as well.

SOURCE: 1998 pontiac grand prix starter

disconnect the negative battery terminal first then disconnect the positive treminal so there are no accidents, raise the car safely go underneath & remove the starter cover should be 3 10mm bolts holding the cover on then remove the 2 through starter bolts 15mm then disconnect the + battery cvable from starter then disconnect the solenoid wire should be a 7 mm bolt. good luck