GMC siera pick up heater switch.

  • 1998 GMC SIERRA
  • V8
  • 135,000 MILES

I own a 1998 GMC Sierra V8 350 engine 4x4 ext cab with power everything and air con-. Since the purchase of my truck there has been an electrical issue with the heating system. The fan will only run on high and will only run if the switch is in the on position prior to starting the engine. And I’m not sure but the air conditioner recently stopped working and my speed control stopped functioning as well.

Here is a list of everything I have done trying to resolve this problem.

1. I have replaced the fan switch twice.
2. I have replaced the fan relay switch twice.
3. I have replaced the heater resister twice.
4. I have replaced the fan motor once.
5. I have replaced the main fan fuse under the hood.
6. I have replaced the fan fuse inside the cab.
7. Recently I took the entire dash out and physically inspected the wires.
I tested each wire from the harness that runs the fan in each position and found each wire working with my test light.
8. I noticed that the hot lead going into my old fan motor to be somewhat burnt
So I installed a new male plug when the fan motor was replaced.
9. I purchased a used control panel and replaced the original one.

After disassembling my dash several times I’m left baffled as what to do, I am hoping someone has seen this scenario before and were able to resolve it. I have to
Keep a window partially rolled down to regulate the temperature inside the cab on cool days and suffer with no air conditioning during hotter days.

Someone please help me.

P, S.

After the last time the dash was r and I’d my ignition switch is now stuck and unable to click back far enough to pull it out, It does function the other direction enabling it to start the engine.

Do you
have the same problem?
Tuesday, March 15th, 2011 AT 10:40 PM

1 Reply

When you say heater resister, do you mean the blower motor resister?
Was this
Wednesday, June 15th, 2011 AT 4:09 AM

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