[LPete]

Pepi, why don't you post it? It can't hurt.

I don't get the connection from the high blower relay to the clutch. That doesn't make any sense to me. I do see the ambient switch in John's diagram -- I'd bet the green/brown two-wire connector goes to it.

[vidguy]

Thanks guys for the support.
Charles there is no AC wiring in my manual.. that's all I have. I also have what JohnTA posted. Thanks John! BUt it is not that complete.. either.
Pepi:
"If you look at the picture JohnTA posted, there was a fuse at the blower resistor. I'll bet this breaker was installed in place of that fuse. Many GM cars had that fuse at the alternator, but I'll bet on this car it's back at the firewall instead."
That's exactly right. There was a FUSE where that Circuit Breaker , which I installed, is now. My Compressor blew that fuse 2 or 3 times before the clutch failed once a few years back. I replaced it with that circuit breaker when I had the Compressor repaired. And the the Circuit Breaker had yellow leads.
It does work and jumping that connector made no difference.

I went back out and completely unwrapped the wires coming out of the relay.
You guys are correct, I was mistaken.
Here is what I found:
1) The RED wire out of the Relay IS connected to the STUD on the Alternator. It
has a fusible link on it in the loom near the alternator and it changes from RED to BLACK and the BLACK part of the wire is on the stud.

2) The Connector on the Alternator has a BROWN wire and a Red wire. I thought the BROWN wire was GREEN. It is not. AND the RED wire on that connector is NOT the same RED wire from the RELAY, as I thought. It too has a fusible link on it, and at that point, it changes from RED at the Connector to RED w/ Black Stripe in the loom. That goes to the Bulkhead connector.
so.. It looks like the wiring is correct just the wrong colors...
Ill take a photo of the THERMAL SWITCH right now.

[vidguy]

That BROWN wire to the Thermal Switch is the BROWN wire from the relay.

[LPete]

Originally Posted by vidguy

That BROWN wire to the Thermal Switch is the BROWN wire from the relay.

Are you absolutely sure? I suspect the brown wire from the two-wire green and brown connector is actually the brown wire at the thermal limiter. I'd bet the green wire goes in through the dash to the control unit.

It makes no sense for that brown wire to go from the relay to the clutch circuit.

[LPete]

I'm willing to bet that the brown wire at the relay is the wire that's grounded to the firewall in John's diagram. That wire needs to be grounded to turn the relay on.

[vidguy]

You could be right.... there are 2 wires grounded to one screw on the firewall.. I'll check in the AM it's too darned dark to see for sure right now..

[Pepi]

That brown wire IS the power to engage the clutch, it goes through some switches (ie ambient switch, control switch). Then without looking at a correct wiring diagram, the relay (if that is truely correct) to the "B" terminal of thermal limiter, where it comes out the dark green "C" to the compressor clutch, and the black off the compressor clutch provides the ground to engage clutch. The other black wire on thermal switch (Superheat Shut Off) will cause a short which will blow the little fuse inside thermal switch rendering no power out of the dark green wire.

I'll scan the info I have for my 73 today/tonight and post.

[LPete]

Pepi, you have it nailed.

To beat a dead horse:
The high blower relay has four connections:
1) power in from the alternator (red)
2) power out to the resistor/fan motor (brown/orange)
3) power in to the relay coil (gray, from the fan switch)
4) ground, to energize the relay coil (I'm assuming brown)

I don't see it making any sense that this relay has anything to do with the clutch. There must be two brown wires -- one from the ambient switch to the thermal limiter, and one from the high blower relay to a ground somewhere.

Assuming the gray wire is hot (and it looks like it is from the measurements posted) grounding the brown wire at the relay should energize the relay and turn the blower on high. If it doesn't, the relay must be bad. In any case, connecting B+ and ground to the relay terminals with the gray and brown wires should make the relay click.

The '69 diagram I have shows the relay with only three terminals -- the relay housing provides the ground. I'm assuming that the relay on this '75 is screwed to the fiberglass heater housing, so it needs a separate ground wire.

[LPete]

Here's a '69 A/C diagram. It should be very similar, other than not having the thermal limiter and wiring, and having the high blower relay coil internally grounded.

[LPete]

We never talked about the low-speed problem. The black/red wire at the resistor should be hot from the fan switch in low. If it is, and there's no power coming out of the resistor to the blower, the resistor is bad.

[vidguy]

Thanks again fellas for taking time to help me with this very common problem....

Here is a diagram I jsut made here at work. I believe it is correct to what I have. I have the car out front. It may not be correct to the manual.

Note that in my resistor (large one?) the Yellow/Black and Black/Orange wires are on the same terminal.

Again, If I jump the two wires as I show, with a paper clip, I can get fan on HI, BUT.... I get it even with the KEY OFF..
So it seems that something is not triggering the Relay? I tired Grounding the AC compressor ground but that didnt help.

I checked the control head, and on HI, I am hot at the Orange wire at the switch.

[LPete]

My post (28) tells how to test it. Power to gray wire, ground to brown wire, relay should click, fan should run.

[LPete]

James, 12 v on the gray wire and 12 v to the fan *is* high speed. Are you saying that's how it is in position 3, not "hi"?

[vidguy]

Lpete-
There are 4 positions on my switch. Of course the Lowest would seem to be OFF.
But it says LO

James, 12 v on the gray wire and 12 v to the fan *is* high speed. Are you saying that's how it is in position 3, not "hi"?

I'll go double check that now.
In Med Hi (3rd of the 4 positions including LO/Off) I have power on RED GREY and BLACK ORANGE)
In Med Lo ( 2nd of 4 positions including LO/Off) I have power on RED, GREY
THese positions run the fan as they should.

How would I test that as you described?

grounding the brown wire at the relay should energize the relay and turn the blower on high. If it doesn't, the relay must be bad. In any case, connecting B+ and ground to the relay terminals with the gray and brown wires should make the relay click.

Would I try to ground the brown wire? with the Key on?

I went out and accidently jumped the Red and Brown with the Paper Clip.. YOWWWW
Burned my hand! Dont DO THAT!

[LPete]

Originally Posted by vidguy

Lpete-
There are 4 positions on my switch. Of course the Lowest would seem to be OFF.
But it says LO

I'll go double check that now.
In Med Hi (3rd of the 4 positions including LO/Off) I have power on RED GREY and BLACK ORANGE)
In Med Lo ( 2nd of 4 positions including LO/Off) I have power on RED, GREY
THese positions run the fan as they should.

How would I test that as you described?


Would I try to ground the brown wire? with the Key on?

I went out and accidently jumped the Red and Brown with the Paper Clip.. YOWWWW
Burned my hand! Dont DO THAT!

You shorted battery power directly to ground when you did that. Hopefully the ground wire is still OK, and you didn't burn it out by doing that.

All it takes for the blower to run on hi is battery power on the gray wire. With the key on or off, you should be able to jump between the red wire at the relay and the gray wire at the relay, and the relay should energize and feed power to the blower. Can you check and see if this happens?

[vidguy]

With the key on or off, you should be able to jump between the red wire at the relay and the gray wire at the relay, and the relay should energize and feed power to the blower. Can you check and see if this happens?

Worked as you described!

You shorted battery power directly to ground when you did that. Hopefully the ground wire is still OK, and you didn't burn it out by doing that.

No,the Brown wire is still fine. I'm certain that all of the heat generated by doing this was spent through the Paper Clip and was released in the burning of my flesh...

[LPete]

I've never done anything stupid that hurt...

You've verified that the whole high-blower circuit works. As long as the fan switch sends power out on the gray wire, the blower will run on high.

You said earlier that the gray wire has power in the "3" position, then you said "2 and 3". If that's really true, the blower is running on high in those positions. That would seem to be a problem with the switch.

In the other positions, the fan switch sends power out through one of the other wires to the resistor. Only one wire from the switch to the resistor should be hot at a time.

If my diagram is correct for your car (and I believe it is), the black/red wire should be hot in lo, the black/white in "2", and the blue/white in "3". You will see voltage on all the wires at once, but only one will have battery voltage (the others will all be lower than battery voltage). If this isn't true, you have something wrong with the switch or the wiring from switch to resistor.

If you unplug the connector from the resistor you should only see one wire with voltage on it at a time.

Edit: I wanted to add that the object you called a "small resistor" in the clutch circuit is actually an ambient switch that prevents the compressor from engaging when the weather is cold.

[vidguy]

Thanks
The speed of the fan is distinctly different at the 2 settings on the switch that do work inside the car.

It's clear it's running on "a lower" speed at one setting and a "higher Speed" on the other setting. Then, I push it up to HI, and it stops.

Ill go verify if it's the GREY wire that has power in the 2 of 4 and 3 of 4 positions
Hang on.

[Pepi]

Boy you guys have done a lot of work today, just trying to catch up on the post! Way to go! Lee you have helped him a lot, with the jumping of the red and grey you have verified the relay works. He should only have power to the grey in HIGH position.

I have a wiring diagram for a 75, I am working on getting it scanned into the computer right now.

[Pepi]

Okay, here is the scanned 1975 wiring!! Hot off the press!!

I stand corrected on my advice to get rid of the circuit breaker/fuse and go with a regular wire. I see 1975 has a fuse there and not at the Alternator.

Looking at the diagram, and I think my 73 shows the same, it appears the low speed has power going to it at all times, the 16GA BLK/RED at the blower resistors UNLESS the master switch is turned ON.

I have tried uploading both JPEG and PDF, we'll if they both work. If you want, PM your email address, and I can send the PDF version to you, so it is easier to read, and print off.