My controls are no longer working, and my heater core is no more. What I'm interested in doing, is a simple
on/off switch for teh compressor, and a rheostat style switch for teh blower speed control. I'm not worried
about teh air blowing out of teh bottom vents, only teh top....I sell HD switches, so that wouldn't be a prob.
How would I go about running power to teh compressor? Can I just run a 12-14 gauge wire (with a circuit
breaker of fuse) from teh switch directly to teh clutch cycling switch?

Electrical is just not my gig, so pardon my ignorance....

 

It's not mine either (and I'm dangerous with a soldering iron), but the electrical circuit to engage the compressor is fairly simple - You need power at one end, a ground at the other. Power source should be fused, preferably about 25 amps, run through your switch (with appropriate ampacity) out to a High Pressure Switch (mounted on the High Pressure Line so that it opens when the pressure gets high enough to blow a hole in the hood); onto the Low Pressure Switch (mounted on the output from the Evaporator which will open the circuit when the pressure is low enough to ice things up) and finally on to the compressor clutch coil - the other side to ground. Difficult part #1 will be maintaining radiator fan control at idle and low speeds. Without the fan (or fans - depends on Year), you will open the high pressure switch (or blow up the system) long before your thermostat opens or the fan otherwise comes on. A/c fan control is handled by the ECM based on input from another switch on the high side line - or pressure sensor mounted in the same place. What you currently have depends on the Year. Difficult part #2 is idle control. Without a signal to the ECM that the compressor is engaged, it won't know to increase idle speed - so it's going to stall, surge or just generally idle like crap. That signal was from the Controls and depending on whether it was a Manual or Automatic Control system, it was either 5 or 12 volts and the later Years are even smart enough to delay compressor engagement a nano second so that the idle remains incredibly stable. And if you can't Overcome that later arrangement you're idle is still going to surge. To pull this off, you should purchase the Service Manual for your Year so that you can see what the circuits are - or you can contact one of the a/c aftermarket suppliers that cater to the rod guys (try Street and Performance www.hotrodlane.cc) as they probably have a stand alone that will make it all work - or hell just buy the stuff that came with it and plug it back in.

 

PS - if yours is a '90 or up, this gets easier - assuming everything under the hood is intact. All you need is for your switch to run to the right ECM pin and it will do everything else, as these Years use the ECM to drive a compressor relay. You'll still need the Service Manual for the ECM pinouts and the correct voltage - most of the inputs are around 5 volts and if you send too much, you'll fry the ECM.

 

Hmmm...mine's an 89....I'll have to decide whether I want to risk this
just to have a/c on teh weekends....

 

Do you have the electronic control? If not, I'd think it would be easier and about as cheap to replace the manual controls. Don't worry about the heater core-since you are in AZ.

If you have the electronic A/c control, I'd still think about replacing or looking at the control head. I had some problems with mine (electronic) and ordered a new control head (with the buttons, etc) so I could R&R. the head was only about $170, so I just got one, after I'd replaced everything, I took the head apart and found one of the circuit boards had come loose from an input cable. If I'd taken everything apart and looked at stuff, it would NOT have cost me anything.

bill

 

What are HD switches?
I'm in a similar situation. I took the "suitcase" off of the firewall and want to replace it with a slimmed down version that still has the blower motor in it. I want to be able to run the heater.(Moving to Wisconsin in a couple of years). I want to be able to control the blower motor and the hot air. Is this a hijack if I ask for help klike this in here? Seems along the same lines.