So I have been rummaging thru the threads but am in need of a starting place between the fan switch itself and the resistors that set the fan speed. And anything else that may be in between.

Maybe a year ago my fan speeds 1 & 2 quit. 3 & 4 worked fine. I could live with that.

A few days ago 3 & 4 quit. So no fan at all.

All fuses appear good inside and under the hood.

Does this failure sequence lead to something specific?

Is it bad connections at the switch?

I have been working on the HVAC system on and off with problems with the diaphragms but thought I had that settled. The lines were all redone and worked good. Since then, I had the leaky xfer case seal which is now fixed, but wound up with fluid in the 4x4 diaphragm under the battery which i replaced as well as the vacuum switch on top of the case.

The HVAC vacuum switching system seems to be failing now also so maybe I sucked fluid up into the lines under the dash. I have not checked yet. But my main concern now is getting the fan to work so any thoughts are appreciated.

2001 ZR2

 

To help out, we'll need to know if you have the Computer Climate Control system or the manual system and what sort of transfer case, the 3-button or 4-button. The former will indicate what sort of blower motor control you have and the latter indicates the vacuum line setup. It sounds like you addressed the vacuum lines already.

For the manual HVAC system, there is a resistor network that can be accessed from the engine compartment. It drops down into the top of the air box after the AC evaporator. I have the computer controlled system so if you have the other, I don't have any first-hand knowledge of that circuit.

This is a link to the part at Rock Auto that you might need to replace:
https://www.rockauto.com/en/moreinfo.php?pk=85567

Here's a video that shows the location of the blower motor resistor.

 

I believe it is a manual HVAC system and a 3 button xfer case.

Just was reading a thread about all this with lots of input from "George" and it kind of got my head spinning. Going out to mess with it today...

 

Oh Oh, did not mean to overwhelm. Let me know if I can clarify but Christine should have you covered.

George

 

Hello George, Just trying to clarify the correct relay for the blower motor. Seems the 87 and 87a terminals can be switched and sometimes there is an 86 terminal reversed with the 85 terminal. The GM OE ones are 4x as expensive as after market but the only after market that matches is a month out. Any recommendations?

Thanks.

 

Is this manual or automatic HVAC?


George

 

Manual

 

The purpose of the relay is to route the fan speed choice through the resistor network for the lowest three speeds but switch to straight power without any resistor(s) for the highest speed. There are two fuses to check: HVAC Fuse 30A in the UHFB and HVAC fuse 9 in the IP fuse block. The relay needs to be a proper 5 pin with 87 and 87a. 85 and 86 can be reversed with no issue. 30 needs to be 30. If 87 and 87a were reversed then you would get full speed on selector switch positions 1-3. Looks like rock auto has the correct 5 pin for under $10.

George

 

My fan quit the following was my fix.There is a connector with four wires that had overheated, causing a bad ground connection. It is very close to the fan under the hood. A visual inspection can find the problem. I bypassed the connector with one wire, using a new one-wire connector, leaving the other wires intact.