AC Button light connection
 

So on my 82, I have a button in the middle of the fan knob. When it is pushed, it
clicks in, the light in the middle of the button lights up, and the AC turns on. I
assume it is the same for all S1/S2's.

Question is, I want to use the AC button as another button. I want to tap into the
output wire, which I guess is the wire going from the AC and into the engine bay. I
am looking at the wiring diagram for the 82, section g. I can't tell what/which wire I
am looking for, so I believe that it is the refrigerant pressure switch (G21)? I would
think it would be a power wire into the button, and when it connects it turns on the
button light and sends power to an AC solenoid somewhere. Yellow/blue would be
inbound and yellow/red would be outbound/everything on?

http://i41.tinypic.com/34rarll.jpg

You're close; The button actually switches ground, not power, and only provides a ground when the fan switch is not off.

The "magnet clutch" at the bottom of the page is the unit on the compressor that your button ultimately turns on. It's controlled by the air-conditioning relay, which is under the hood near your brake booster. Button switches relay, relay powers clutch.

The signal passes thru the "Frost Temp Warning Switch" and the "Refrigerant Pressure Switch" on the way (they have to be closed for the AC to run), and there's a diode reverse-biased across the relay coil so it doesn't damage stuff when it opens.

The grounding signal goes G-15 > G-16 > G-20 > G-21 > G-20 & splits to G-18 (relay) and G-23 (diode) at that point. recombines at G-16 which goes thru X-02 to the fusebox.

If you only need to control a small amount of power (swith was only designed to run a relay and the lamp, remember), you could bypass most of that.

Cool. I am trying to get the jist of that :)

I have no more relay's on my drivers side shock tower. I was going to use the button as a
signal wire for a relay I will be using for other than AC purposes.

If you are using your own relay, You'll want to bypass the frost warning and pressure switches completely with shorting jumpers, and just wire your relay's coil in at G18's YL and LB leads; you'll be good to go.

Having deleted my AC, it would be really cool to use that AC button to turn on the rear window defogger.

What is a shorting jumper?

I would like to just pull the center console out and use one of the wires from the
back of the button. When I removed my AC, I removed all the wires in the engine
bay concerning it all the way to the firewall. Either way I will have to get under the
dash, just trying to find the easiest course of action. I thought I could just pop the
console out and take the outboard power from the button and run that into my
signal on the relay (86).

Shorting jumper = piece of wire that replaces the switch, "shorting" it closed.



The flat-simplest way to use that switch to run a relay is to disconnect the LG wire from G-15 completely (tape it off, it's a +12 lead)and connect your new relay (and a reverse diode!) across the terminal that the LG wire came out of, and the existing LB wire.

That lets you abandon/remove the old AC relay (which you said is already gone) and the pressure and frost switches, and the old diode.

The diode across your new relay is important to keep the back-emf that comes out of the relay coil when it's disconnected from causing problems, like arcing your switch contacts.

Lemme see if I can sketch it for you...

http://img.photobucket.com/albums/v2...ff/Sketch1.jpg


Keep in mind... the AirCon button only works if the fan is on. That's how the inside of the fan switch is designed. Changing that would require disassembling and modifying the inside of the switch.

Oh, and if you want to switch the 12v going into the new device instead, that's cool too... just put the relay contacts between the power source and the new device. Otherwise no change.

Ok, so that will be out then. I was going to use it as my fuel pump switch, but seeing
how I have to have the fan on all the time, it would suck. Guess I will just use my old
fuel pump leads as the signal :)

Thanks DD!

EDIT: Would it be a good idea to ground the pump through the stock harness ground?
I want to ground the pump to the frame rail, so I only need the + wire on the original
harness. Snip the old ground on the harness or ground it to the frame as well?

Well, I put the relay in and got everything wired up. Turn on the key and pump
runs, turn the turn signal on and the pump cycles with the light. Guess I have
to ground the pump to the frame and get it completely off the OE harness.

Reran the fuel pump's ground to the frame rail. Now I can turn on my blinker and the fuel pump
stays constant. The volt meter still wags back and forth, but not as much now.