[vidguy]

OK thanks. I'm going to print out Pepi's diagram and verify it against what I have.

[Pepi]

Originally Posted by vidguy

Let me clarify that last statement
in position 3 - GREY wire IS hot at the relay
in position HI - GREY wire is NOT hot at the relay.
I know it sounds backwards..

Here is a pic of the Control plugged into the Connector and a legend as I see it:
engine compartment on left - A/C control Harness on right

GREY ----------------BLUE
BLACK/White---------TAN
BLUE/White----------ORANGE
BLACK/RED-----------BROWN/White
GREEN --------------GREEN

Definately backwards, you need to de-pin (for a better lack of words), the blue and orange and swap them. It should go as follows:

GREY-----------------ORANGE
BLACK/WHITE---------TAN
BLUE/WHITE-----------BLUE
BLACK/RED------------BROWN/WHITE
GREEN----------------GREEN

If you look at the two pictures, you will see I have the 77 colors called out and marked HI, MED HI, MED LO and LO, In the 1975 picture I have them labeled also, but didn't need to color the wires, because the color call-out was the same as yours. Disregard the GREEN----GREEN, I didn't label those because that is for the compressor turning on.

This will fix your problems, since you found the broken resistor.

[vidguy]

Guys,
I swapped the ORANGE and BLUE wires.
I now get HI!
And if I jumper the broken resistor with some 12 gauge wire, I get Low on Lo!
Thanks SO much for sticking with me on this!
You're help has been unbelievable.

There are still a few things that are not just right though, and I think I won't get them right unless I convert the Engine harness to the 77 design. Mainly the 5 terminal Relay from the 75 style 4 terminal Relay.
I'm studying the wiring diagram closely.

I found someone that has a used Resistor so I will buy that.

Here are the remaining issues:

1)With the lever on MAX A/C Only LOW fan works--It was a few hours ago, and I think that's right... I lost my note... I'll recheck that in the AM..At any rate, I'm certain that HI still doesn't work in that position, I think it was running LO with the resistor jumped.

2)It appears that the two MEDIUM speeds are identical.

I tried both 77 style controls and switches and both act the same way.

Again Thanks Lee and Pepi SO MUCH!!
I hope I can return the favor.

[Pepi]

Originally Posted by vidguy

Guys,
Here are the remaining issues:

1)With the lever on MAX A/C Only LOW fan works--It was a few hours ago, and I think that's right... I lost my note... I'll recheck that in the AM..At any rate, I'm certain that HI still doesn't work in that position, I think it was running LO with the resistor jumped.

2)It appears that the two MEDIUM speeds are identical.

I tried both 77 style controls and switches and both act the same way.

Again Thanks Lee and Pepi SO MUCH!!
I hope I can return the favor.

The max A/C only working on low, does that still have the wire in place of broken resistor? Because with resisitor broken the fan should not be working on low ever.

When you goto MAX A/C, you should be getting power out of the #1 terminal of the 77 control head. I am not sure what color wire that is, but it should tie in somewhere with the orange wire you had to swap. Actually just looking at wiring diagram, (this is hard because your wire colors don't match the diagram), We need to find out what color wires have power when in the MAX A/C position.

Somewhere there should be two wires together, either the ORANGE or BLUE (I am guessing) That should be the wire for controlling relay. We might have to switch ORANGE and BLUE back, and switch wires on the other connector, the GREY and BLUE/WHITE.

But like I said, The BROWN, GREEN/WHITE wires will have power in MAX A/C, but there should be a third, either ORANGE or BLUE. Maybe to help disconnect the connector going to fan switch, that way whatever spped the fan switch is in won't effect the results we are looking for.

[LPete]

I don't know if this will add anything to the discussion, but as far as I know, Max A/C has nothing to do with blower speed -- all it does it switch the air intake door to recirculate inside air instead of bringing in outside air. I could be wrong, though.

I haven't taken the time to figure out which resistor is broken, but if it was replaced with a piece of wire, at least two speeds will be the same. It is true that the blower will never run at its slowest speed with the resistor bypassed, but the motor will run with the switch in low. You're probably way ahead of me at this point...

Edit: Now that I looked at the pdf version of the '77 diagram, it does look like the high blower relay is turned on via the gray/black wire from the mode switch in Max A/C. That mode switch diagram is a little hard to decipher...

[Old Goat 67]

I don't know if this will add anything to the discussion, but as far as I know, Max A/C has nothing to do with blower speed -- all it does it switch the air intake door to recirculate inside air instead of bringing in outside air. I could be wrong, though.

You are correct.

[LPete]

Again, if it helps, they switched to a double pole relay (thus the five pins). On the '77, the blower power always runs through the relay -- when it's energized, the bottom contact (hooked to the red wire) feeds power straight to the blower motor. In the other positions, with the relay de-energized, the variable power out of the resistor feeds through the upper contact to the blower feed wire.

I *think* you can disregard the dark blue wire into the '77 relay, since you have the connection straight from the resistor to the blower. The '77 is just a little backward from the '75.

[LPete]

Originally Posted by Old Goat 67

You are correct.

I think I was wrong on this '77, though. I don't remember seeing this before, but it looks clear that in Max A/C the mode switch energizes the high blower relay.

[vidguy]

Once again, thank you Gentlemen!

The MAX A/C only working on low, does that still have the wire in place of broken resistor? Because with resisitor broken the fan should not be working on low ever.

Yes that was with a wire jumping the Resistor. (new one on the way)

Lee, From my analysis of the Connections on the lever switch I agree that the MAX A/C position does affect blower speed. And separately the vacuum "head" closes the Kick Panel Door.
I drew a diagram the other day of the continuity on the control head in the various positions. I haven't noted what is hot on that switch yet when all is hooked up, so I dont know if my OHM readings at the workbench will help but..

The two '77 A/C harnesses/connectors I have both have 3 terminals that connect to the control switch (Rotary Switch).
They connect at terminals #2 #3 #5
#2 = Yellow (power from fuse block)
#3 = Green (AC compressor thermal switch)
#5 = Brown White ( one goes to the ALWAYS HOT terminal on the fan switch one goes to the Brown/White terminal on the connector that attaches to the Engine harness.)
That is the wire that should be hot on MAX AC I think.

ON the MAX AC position
Position 2 (MAX AC) Terminals #5 and #3 show continuity - That would be POWER and AC Compressor
On all other Lever positions, Power is going to terminal #2 as well. That's the Brown/White wire to the Relay I believe.



Here are some pics of the wires.

[Pepi]

It almost seems as though you are missing a wire. Where does or how does that brown/white wire hook upto the connector pictured the other day? It must change colors I am thinking. According to the wiring diagram it shows 4 therminals being used on the connector for the control head. I am thinking the dual brown white needs to goto terminal one. Check continuity between terminals 5,3 and 1 when in MAX A/C.

[LPete]

I'm suspicious that they didn't actually install the extra wire (914A gray/black) to run the blower on high in Max A/C. That wire's (apparently) missing at the mode switch and at the fan switch connector (there should be two wires instead of one at the fan switch). That would mean that the 912 red/white circuit at the mode switch would have to be hot in Max A/C as well as all the other positions.

If you look at the drawing of the connector to the left of the switch, I'm fairly sure that it's drawn as if you're looking into the connector from the terminal end. If that's true, pin 5 should be hot from the ignition, pin 3 should be the compressor feed, and pin 2 should be the blower feed. It sure seems like wires have been swapped around.

[LPete]

I guess the bottom line is that I'm thinking that there should be continuity from pin 5 to pins 3 in any position that requires the compressor to run (don't forget defrost), and pin 5 to 2 in all positions except off.

[vidguy]

I agree it does seem like a wire is missing.. Can anyone verify their wiring harness on a 77-80 Firebird with A/C?
When I get home from work I'll check this out.

Both my 77 and what I belive is a 78 harness are the same in this respect (connectors - control head) They dont look tampered with and I bought them from 2 different people at 2 different times.
Of course the 75 original is entirely different..

[Pepi]

Originally Posted by vidguy

Both my 77 and what I belive is a 78 harness are the same in this respect (connectors - control head) They dont look tampered with and I bought them from 2 different people at 2 different times.
Of course the 75 original is entirely different..

What!! Your killing me, a 78 harness now!! LOL

Yeah that additional GREY/BLACK wire coming off I think #3 terminal seems to be missing. But What is weird, according to your picture you have a single yellow wire coming from fuse panel to the selector switch, and the wiring diagram shows a double brown. Does that yellow splice off to the connector you were first picturing? (We need to come up with a good label for the different connectors so it is easy to specify )

I can try to look at a 78 wiring diagram tomorrow, maybe that is were a lot of these differences are, with wire colors, and quantity.

No matter what, we'll get this problem licked.

[vidguy]

Pepi! Im guessing there.. I KNEW that was a baddd thing to say..
Yes there is only one hot lead to the control. It is a Brown wire from the Fuse block that connects to the Yellow wire on the Rotary Switch connector.
Now I only say that about the harness being a 78 because I discovered one difference.

I have 2 A/C control Harnesses that go under the dash on the control.
I have been using both as tests. One I really believe is a 77...
I have 2 identical 77 Control heads. I have been using both of them as tests to assure that the switches both work the same.

I realized, after I went to switch the BLUE and ORANGE wires on the connector that attaches to the Engine Harness as you guys suggested. (I did that on both so that everything was the same.)
that one harness is different in ONE respect:

Harness "A":
There are 2 BROWN/WHITE wires coming out of the Rotary Switch terminal #2.
On this harness the second BROWN/WHITE wire goes to the position on the Connector that attaches to the Engine harness which is always HOT.

Harness "B"
On this harness, only one BROWN/WHITE wire coming off of the Rotary Switch terminal #2. It's Engine Harness ALWAYS HOT connector is powered by the Rotary Switch Terminal #5 which is a jumper of the single YELLOW POWER LEAD from the Fuse Block.

I attached comparison pictures.

Now the status:
If I jump Rotary Switch terminals #5 and #3 as suggested, and I use the Harness that has the 2 BROWN/WHITE wires coming off of terminal #3, and the ORANGE and BLUE wires are still swapped....
I am very close..
I get HIGH on Rotary Switch/Lever position MAX AC!
And, the switch controls it meaning I can turn the Fan Off at that position.. but I also get FAN speeds on Rotary Switch / Lever position OFF.
I don't think that is correct.. But it's good news.!
One other weird thing that I noticed tonight.. I dont get the Medium High speed with things wired this way. (But I dont have the resistor jumped tonight) I get speed 2 and HI. No fan switch position 3.

I can't tell yet if the compressor is getting power when it should (AC and Defrost) but Im pretty sure that wire path is working.

I would like to verify that someone else's 77/78 A/C Control harness rotary switch connector only has 3 terminals with wires on them. I cant beleive that both of these harnesses are missing the entire wire and terminals on the rotary switch. And Where would that wire go anyhow?
It's CLEAR that the control rotary switch is for an A/C car so unless on both of these the Rotary Switch has been changed.....

I have an entire extra Engine A/C harness. I cant be sure, but I think is a 78 harness with a 5 terminal relay connector. I am going to rig that up as soon as I can, now that I got my new relay and see what happens..

I hope to get my replacement resistor by the weekend.

Thanks guys for the patience...

I'll continue to try anything to get this correct.

I'm going to post separately for confirmation of the rotary switch terminals and the way the fan switch acts at the different positions.
Note that in the picture below one of the connectors that connects to the Engine Harness is STILL swapped BLUE / ORANGE. That was the one I tested with tonight.

[Pepi]

I'll have to look at it more later this afternoon, but that is really weird with the missing wire. The harness with the two yellows at terminal 5 looks more correct.

It sounds like more swapped wires, with fan working on position 2 and not 3. In position 2, power should be going through two resisitors, and in position 3, power going through 1 resistor. So with a broken resistor, position 2 should not be working.

Like I said, I'ly to copy of a 78 wiring diagram today and compare.

[Pepi]

Okay, some good news, and some bad news. The good news is We are finally figuring this out, the bad news is it appears as though you DO have a 78 harness, and really bad news I think you have a 79 also.

I have a copy of a 78 wiring schematic, and it shows two yellow wires on selector switch, along with light green and brown. According to 78 the yellow wires, one come from fuse block, and the other goes to BLACK/RED on the 75 harness to run the fan at low speed always. So unless the fan speed switch is selected on any other speed to overrride low, low is all you will get with selector switch on MAC A/C. That and the wire colors match what you have.

In 79 Pontiac would not supply the wiring diagram for firebirds, but I looked at one for a Corvette, and Oldsmobile, and I saw 2 brown/white wires, 1 yellow, and 1 light green. That is why I think you have a 79 harness.

I've got the wife making a copy at work trying to enlarge it for the 78. I'll post it later tonight.

I think once you get the replacement resistor, we'll be able to see exactly how it is working, and what speeds are what.

[vidguy]

Thanks Mr. Pepi!

According to 78 the yellow wires, one come from fuse block, and the other goes to BLACK/RED on the 75 harness to run the fan at low speed always. So unless the fan speed switch is selected on any other speed to overrride low, low is all you will get with selector switch on MAC A/C. That and the wire colors match what you have.

That sound's like where we are at!

I'll do what I can until I get the Resistor.
I am going to try to test install the entire extra AC engine harness if its possible. I think its a 78.....
So I dont have to remove the harness from the firewall and all that, I'm thinking of running a LONG wire from the FUSE Power and just loosley install the Harness and controller in the engine bay with my new 5 terminal relay. and see what happens!

[Pepi]

Just out of curiosity, why do you want to go with the 5 terminal relay?

[Pepi]

Originally Posted by vidguy

Thanks Mr. Pepi!

That sound's like where we are at!

No problem, glad I can help.

Like I promised, here is the copy of a '78.