1998 GMC Sierra C1500 HVAC system

[SG3000]

I've looked around but there's a lot to search for and I can't seem to find my issue just yet so figured I'd ask.

 

My blower only runs on High and one day during the winter of last year, I had smoke in the cab and the HVAC wasn't working at all. I did not think to check the fuse for the blower under the hood, because the smoke was in the cab and not coming from under the hood. 

 

So what I've done so far recently, this is months if not a year after the smoke and blower stopped working,  is replaced the resistor, since I found that it was a common issue for the blower only working on High. After I replaced it, the blower would then only work on the two settings between Low and High, but wouldn't work on Low or High. But that lasted for like a day and I had replaced the Relay and the entire blower+fan itself. 

 

I finally checked the fuse under the hood, it was bad, but when I replaced the fuse and it was a 50A fuse, the blower started working again but only on High.

 

I got a new switch coming, which is probably unnecessary now but either way, I don't understand what the issue is.

 

To summarize

1. Would only work in High until something burnt up and it stopped. 

2. Replaced the resistor and it started to work on two settings between Low and High but not work on either of those two. 

3. It then stopped working all together again. Fuse was burnt out, replaced it and now it only works on High again.

 

I may have forgotten to remove the fuse before replacing the old blower with the new one, but I am certain that I had pretty much everything disconnected at the time. It also looked like it's been replaced before but I'm uncertain.

Edited November 9, 2024 by SG3000

[richard wysong]

Did you replace the wires and connector to the resistor? common failure, most new resistors come with a repair harness. It is also possible a bad blower motor fried the new resistor

[SG3000]

I only bought the new resistor from Rockauto, not the kit that would have came with a new wire harness and connector.

 

The blower is also from the same site and has a PASS sticker on it, so I assume it was fine and it does work on the High setting.

 

But if the resistor did get damaged because I read somewhere that you're supposed to remove the fuse before you replace anything, then I'll try ordering the resistor with harness and try my hand at that mess.

[SG3000]

It's a little frustrating and I also need to try to explain this better. 

 

I replaced the resistor and it would work only on the two settings between Low and High but not either of those two and even though it worked in between, there was no difference in speed at all and it sounded like it was struggling. 

 

So i replaced the Relay and it was still the same. But before i replaced the blower, it stopped working altogether again, which led to me finding the fuse was burnt out.

 

I replace the fuse and it's back to only working on High.

 

Thus is why I'm at a loss. I never had the truck running when replacing these parts, so I don't know how or where I could of gone wrong.

[richard wysong]

It could be the switch where it wasn't working correctly with the new resistor, try that first before buying more parts

[SG3000]

I do already have a new switch on the way already, should arrive next Tuesday so I'll try that next

Edited November 9, 2024 by SG3000

[tbarn]

If you're good with wiring diagrams (not all are), her ya go.

[SG3000]

So the switch came in early and that did nothing but prove it works on High. So maybe the new resistor got messed up, not sure. Or i need a new wire harness and connector for the resistor. That's something I'm gonna have to wait for a while before i get into that conundrum. 

[dna9656]

Sounds to me like a short/bad ground someplace in your heater circuit.

[SG3000]

That's something I've considered looking into, if the new fuse goes bad, as that would give me a good idea if there is a short. 

 

Right now i haven't done anything yet, been busy with stuff and don't get paid until Friday so things have halted for now but i intend to get a new resistor WITH a wire harness and see how that goes.