Is this what you want?

 

Yes, thanks.

 

If you have a specific problem chances are we know how to fix it.

For instance: you are stumped as to why the fan will only run on high. The answer is on the schematic if you know how to read them.

 

This is a 2008 HHR that has no water leaking issues. The resistor and wiring has no appearance of overheating damage. All fuses are good.
For several months the fan would run on Low and Med1, but not on med2 nor high. Confident that this indicated that the issue was the speed control switch, I changed the switch. This did not correct the issue, and I rarely needed the Med2 or high speed, so I did not pursue a repair. Then recently the fan quit completely except for rare occasions when it would suddenly run for a short time. I knew I needed to do some diagnostics and searched for any post that sounded similar to my issue. I also looked for the wiring diagram and was unable to find it. I have a digital volt/ohm meter so I though I would test the resistance of the resistor. The exact specs of the resistor were also not findable on the internet. But what I found was that the resister had no "open" resistors. Next I tested the voltage at the connector where wires enter the fan motor. All speed positions have voltage. But I am unable to find a definitive test for the motor other than wiring it directly to the battery without any circuitry in between. I have not done that.
What I would like to find is any official (or academic) discussion of the possible issue similar to mine and what test(s) I should run with the available tools that I have. I prefer not to cut open wiring harnesses or poke holes into wires if I can avoid it. Far too many of the YouTube videos seem to have the diagnosis invented on the fly by the mechanic who made the video.
Also, if the fan motor is the issue, is the "cut it out with a hot knife" the official repair method used by the dealers? That sure seems an odd solution created by Chevy. I thought those days were behind us.
Thanks for any help you can offer.

 

You say you replaced the switch, did you install a new, or a used, switch?

 

Yes, the replacement switch was new. And after installing that switch there was no change in the symptoms. Erratic operation on Low and Med1. And, as I said, the test of the wires going to the fan motor have voltage at all switch settings except "OFF".

 

A. the switch selects which resistor goes to ground

B. the cut out method is the "official" way.

C . the wire to the fan is always hot and the ground side goes to resistors/switch. Supply ground to the ground side to test the fan and bypass the resistors/switch

D.. there is an off possibility that the splice near the motor has failed, really remote though

 

@donbrew When I look at the diagram that you supplied, it appears that the black wire to the fan is "negative" or ground and the orange wire to the fan coming from the resistor is +12v (positive)". (Am I correct?) In your item C) you state that the wire to the fan is always Hot. Did you mean + Positive hot (ungrounded)? Or did you mean the wire to the fan is always - Negative grounded? I am checking my understanding that you meant the Black Wire is always Hot or connected to ground. And if I were to supply +12v to the orange wire, this would bypass the switch and resistor. And if the fan runs under these conditions then the issue is going to be found somewhere between the power to the switch, the resistor, or the orange wire to the fan.
I have tested the fan by running both + Positive and - Negative wires directly from the battery to the motor and it runs fine. So now I am trying to determine if the issue is on the black wire side, or on the orange wire side which would be the switch or resistor or the wires providing power to the switch.

 

Here is the rest of the diagram, BRN is hot, ORG goes to switched ground.

 

@donbrew This additional diagram was very helpful. I found that the issue is somewhere between the brown wire and the battery. Could you post the portion of the diagram that shows what relay is attached to the brown wire? And are there any other connections between the +12v side of the battery and the brown wire? I ran a wire from the + side of the battery to the brown wire and the fan speed control and the fan work correctly during this test. So, I am half way there.
Again, thank you for your help.