This 1997 GMC C1500 came in for some other a/c service and I asked the customer about the blower working. He said it worked fine and asked why I wanted to know. I told him of the endless requests that I get for information on the blower systems on these trucks and how I wanted to meet my readers needs. He told me to take it apart and take as many pictures as I wanted to.
This information applies to 1995, 1996, 1997, 1998, 1999 old body style C1500 & K1500 Chevrolet and GMC pickup trucks and SUV’s, 1995-2000 C2500 and K2500 trucks and SUV’s, 1995-2002 C3500 trucks, and 1995-2001 K3500 trucks. SUV’s include Escalade, Suburban, Tahoe and Yukon. I will have to break this information into several posts, so please be patient. This part will deal with the blower switch and its signals. To gain access to the blower switch the dash face has to be removed.
Grasp the edge of the dash face panel and pull towards the steering wheel.
When the panel is pulled out far enough, depress the locking tab on the headlight switch wiring and unplug the harness.
As the face panel is worked loose, the switches to the left of the radio and a/c controls will need to be disconnected. Most of the time if the small panel will pull loose from the main panel it will be easier to work with.
It is easier to do all of this with the shifter handle pulled all of the way down to the D1 position.
As the trim panel is rolled away from the dash, the plastic will need to be flexed slightly in order to remove the face panel.
Now that the trim panel is out of the way, the a/c control head can be removed. There are two plastic clips that need to be released. One on each side.
Then the a/c control head assembly can be pulled from the dash.
The latch that holds the harness to the blower switch is on the underside of the assembly. Depress the latch and unplug the harness.
This harness connector is okay of course, but many times the brown and orange wires will be burnt. If there is any heat discoloration, the switch and the harness connector must be replaced at the same time or the condition will return very quickly.
The entire control panel does not have to be replaced if only the blower switch is damaged. There is one screw that holds the retaining plate in place. Remove the screw and retaining plate. There will be two smaller plastic clips that hold the switch to the main housing. Most of the time they will break due to age. That is okay as long as the main retaining plate and screw are installed after the switch replacement. If you need to order this switch please click here.
- Terminal “A” = Light Blue wire, Speed M2, switched power to blower resistor
- Terminal “B” = Tan wire, Speed M1, switched power to blower resistor
- Terminal “C” = Yellow wire, Speed Low switched to blower resistor
- Terminal “D” = Dark Green wire, A/C disable signal, switched power to connector C3, terminal “4”
- Terminal “E” = Empty
- Terminal “F” = Empty
- Terminal “G” = Brown wire, 12 volt ignition supply from fuse #12 (25 amp)
- Terminal “H” = Orange wire, Speed High, switched power to terminal “C2” of blower relay
A/c went out on my 96 chevy tahoe so i installed a new blower motor a new blower motor resister and new blower motor relay but still doesn’t work and came to find out that there is no power passing through the green wire connected to the blower motor fuse is working fine under the hood so im cluless what can i do to make it work
Sorry its the purple wire connected to the blower motor
The two most common things that I can think of for your problem are the blower switch and it’s harness connector that is described in this article and the other two parts of it and a burnt out three wire connector behind the glove box area. It should have a large red, large black and small green wire as near as I can remember.
It varies by year, model and trim level but in general air bag switch or status light, cargo lamp, rear hatch release and 4wd switch
Regarding the picture below this caption: Then the a/c control head assembly can be pulled from the dash.
My question is what are those cords that are wrapped in yellow and black that are not connected to anything for? We found these, 3 to be exact that have nothing to do with the radio or ac connection. Puzzled…
The original blower motor should have had a screw on, 90 degree male terminal. It cannot be attached to one of the mounting screws. The screw will heat up and melt the plastic that the screw is attached to. Instead there is a smaller hole in the blower motor housing near a mounting screw that you will need to use to fasten the ground terminal to.
If you can jumper the switch body and make the relay and blower work then yes, the switch is faulty. Inspect the harness connector carefully though. It is very common for the terminals in the connector body to weaken and not provide adequate contact to the switch terminal.
The information you’ve provided about blower related problems on vehicles like a 1996 GMC C3500 is much appreciated. The blower on this vehicle doesn’t work on any speed, so I have a couple of questions. First, there doesn’t seem to be a place to attach the ground wire on either the old blower motor, or the new one that is now installed. I improvised a ground for testing, but can I mount a spade terminal under one of the screws that attach the motor (after scraping away the paint), and plug into that?
Also, the relay has power and ground, but none of the other wires including the orange wire get power – no matter which speed the fan switch is set to. The relay never clicks either. When I jump the brown and orange wires in the fan switch plug the relay will click though, so does that indicate a bad fan switch?
Thanks again for your articles,
Chris