Chevy & GMC Vans

My high speed fan quit working for the HVAC. Now before you start typing replace the relay.... I already did that one. $32. To quote Cap'n Dave - "NO CHANGE!".

So what else? The switch?

How about a small thermo-nuclear device?

If it's the 91, it may well be the switch. You DID say you replaced the relay. The switch or the motor itself (doubtful about the motor, because it's still working). a trip to the JY may be in order.

It's the 95. But the motor works, at least on the other speeds Capt.

Yup, replaced the relay and it still didn't work.

I just pulled the switch out. I can see a couple of copper places on the switch. With a DVOM, I put the probes on the two places and turn the switch up through the speeds. I get battery voltage UNTIL high it hit. Then nothing. So I am thinking the switch is smoked....

Yup, sounds like it's dead. Time for a new one.

Rats! And I so wanted to see if the small thermo-nuclear device would solve the problem.

It usually does Capt!

2 areas come to mind for this concern - the switch (as has been discussed) & the fuseable link.
The switch puts out power on the orange wire (terminal A) to the relay to turn on the relay. The relay then connects the power from the red wire (terminal 87) to the heater fan motor purple wire (terminal 30).
If there is no power on the orange wire in high, the relay will not turn on.
If there is no power on the red wire when the relay turns on, the fan will not operate.
Oh, there is always a need to ensure there is proper grounds where they should be too.

Given my testing at the switch with a DVOM and getting no voltage at what is shown as A at the switch, does that not indicate the switch itself is at fault?

When the high speed went out on my '96 it was the resistor that went bad.

I have read about this issue before on these sites because one of my vans, a 90, does the same thing. I also replaced the relay, but I had a few laying around for free here.
Anyways , when I read up before about it, One member posted something about the internal part of the switch would heat up enough to make the contacts inside not work well or at all on 'high' because the small metal contacts would 'melt' into the holder a bit and stop making contact. I've never pulled my dead switch apart, but it sounded reasonable enough.
Personally, I have just run mine on M2 for years, and occasionally it will come on for a while, if I leave it set on High. try a used switch.

NotDadsW41 wrote:Given my testing at the switch with a DVOM and getting no voltage at what is shown as A at the switch, does that not indicate the switch itself is at fault?

Correct. No power on the orange wire (terminal A) @ the switch when on high indicates a defective switch. Suppling power (jumper terminal A - brown to terminal C - orange) to that circuit will cause the relay to turn on & give you high speed & confirming the rest of the components/connections are working good.

Well now I am thoroughly confused....

Replaced the switch and no high speed fan still.

Looking at the diagram here... confuses me more. It shows 5 wires going to the replay. I only have 4. I have two pink wires with a white stripe, a green with a white stripe and a black with a white stripe.

The resistor pack I have read should be visible on the outside of the fan box. But I don't see one anywhere...

Is it possible on my 95 that the resistor pack is built into the motor?

On the '96 the resistor is on the evaporator box right behind the radiator overflow and windshield washer bottles. It's on the top of the box. It has a flat wire connector. Easy to get to. I bought a new resistor from the dealer for about $35.00. The new resistor is a bit different so there is a small amount of modding to do to make it fit. Also easy with a small grinder.

Well FML! I've been testing the wrong @#$%@#$ relay! On the 95 there are two up above the blower box on the fire wall. One runs the fuel pump. Not sure what the other does, but it isn't the high speed relay. That one was hidden to the right of the evap box on the firewall. Not easily seen at first. Replaced that and still no high speed fan.

So since I have replaced just about everything else, that means the resistor pack right? <sigh>

I thought from these diagrams that if the resistor pack was bad that the lower speeds would not work and high would work. Is that not correct? Is the resistor pack still tied to the high speed relay that I am not seeing? v8famvan if you have a high res version of that diagram I would appreciate it.

Squid - get the TND ready....

NOT the relays you are looking for in the top left of this photo:


The relay you are looking for is hidden behind the accumulator:


The resistor pack you are searching for: