What's this QWP thing???

[millsroger]

Bottom two speeds on HVAC did not work--digging after the resistors and found a module directly below the glove box with two push pins to the front of the lower dash. It's about 4" x 4" x 1" and marked QWP. Does any one know what it does/is???

 

[THEFERMANATOR]

Sounds like the blend air door motor from your description.

 

[millsroger]

Nope, those are mounted to the HVAC box.

 

[millsroger]

This is silver with a paper tag similar to the ECM box but smaller.

 

[3500GMC]

You're gonna make me go stick my head under my dash aren't you?

 

[THEFERMANATOR]

If it has 2 plugs plugged into it, is a plastic white module, and is directly under your ECM then it is the vehicle speed sensor buffer. Otherwise I would need a pic to tell you what it is.

 

[WarWagon]

Interesting the things under the dash. However it is better to ask a question about the issue you are wanting to solve.

There is a 2 wire connector under the dash by the blower motor that likes to burn up for all years. The solution is to replace the blower motor (FROM GM!) and add a second ground wire from the blower motor to a good ground. Solder the wires if you can as they are at their limit. You get a GM blower motor as they run quieter than the noisy cheap $25.00 autozone stuff. The motor armature from GM has a twist to the design to eliminate clicking at lower speeds.

There are some relays behind the glove box, but, likely your issue is burned out thermal fuses on the resistor pack. They burned out because the blower motor locked up or ran slow due to bad bearings, brushes, or shorted windings. Also a plugged evaporator could overheat them on low speed. you need to look on top of the black HVAC boc to the left of the fan on top for the relays to get out of the way and a plug that goes into the top of the box. This is the resistor assy.

Check for voltage at the motor. Voltage = motor bad. Check for voltage on any connector of the resistor on low speed. Two connections should have voltage. One connection only = bad resistor pack replace it and motor. No voltage is bad relay, connector as described, fuse, or wire. Check the connector first. With high working generally the connections are ok, however, the 2 wire connector is strange when it burns out. Bad motor brushes also act funny and burn out resistor packs.

 

[millsroger]

Thanks war, but nothing in the wiring was burned up or even melted a little. Problem with the blower was the resistor board. For some unknown reason GM added thermal fuses to each of the resistors. Unfortunately they are very close to the coils and in this case two were popped. I found them at a local electronics supply place and replaced them all, $4 total. I also soldered the tabs to the resistor coils and fuses, then offset the fuses so they weren't right above the coils and kind of humpbacked the coils to move them away from the fuses a bit more. Works fine. The module I was referring to is not part of the HVAC system, just found it when pulling the resistor board.