Jason 1979

So i went out to install my new AC solenoid last night and ran into some non-standard wiring.

i do not have the schematic in front of me, but I am pretty sure the diagram below is correct.

The light green wire is spliced into the dark green wire going into the compressor. Dashed light green line.

this to my untrained eye seems to be bypassing a couple of safety features.

my dilemma is that I am in Texas and it is damn hot and the AC works now. If I get in there and they bypassed those components for a reason I will be without AC. This is not a daily driver, so not a huge deal, but I just got everything fixed on the car and want to drive it.

So my choices are,
1) wire in the solenoid and worry about fixing the wiring this winter.
2) fix the wiring and if everything still works, great.
3) fix the wiring and AC does not work.
A) order broken part and fix
B) put the wiring back like it was and worry about it later.

what would you guys do?

speedreed8

All that ac solenoid does is bump up the idle speed at the carb. The dark

green line I think is the correct wiring.

Jason 1979

Yes, but what does bypassing the low pressure switch and compressor switch do to the integrity of my AC system? I assume those components are there for a reason. I have not done any research, but I am guessing that the low pressure switch cuts off the compressor if coolant pressure is low enough to damage the compressor. The compressor switch guess is cuts off compressor if pressure is too high?

speedreed8

Correct they shouldn’t be bypassed. I had to replace both switches on my 79. When I converted to 134a. They were both bad and original.

Jason 1979

Ok, I am going to cut the spliced wire and see what happens. Hopefully everything still works and I can go through that part of the wiring and clean it up.

This is probably the 4th or 5th instance of wires twisted together and covered with electrical tape I have found on the car. I am continually amazed that this car has not burned to the ground.

bmotojoe

The S66 symbol on the drawing is a factory splice. S = Splice 66 is the circuit number. There are many factory splices on our C3's. It's best to get a good wiring diagram like speedreed8 provided for your year car. You don't want the idle speed solenoid wired into the Dark Green wire, it will cycle on/off with the compressor.

Jason 1979

As expected clutch does not kick in now.

My attack plan is as follows,
1) strip the covers off that harness and see how much other damage was done. Hopefully find something else in the wiring to cause the fault.
2) if 1 does not work, get out the multimeter and check voltage before and after the low pressure and thermostatic switches.

That should tell me if one of the switches is bad, I guess I can jump a wire across the low pressure switch if it is bad to check the other. Or vice versa, I don’t remember which one is first in the circuit.

does anyone know a link to a trinary switch for a 1979?

Jason 1979

Wiring harness is all hacked up but appears to be correct. So, solder and heat shrink all of that so that it does not catch fire. Then get out the multimeter.

these things are like multiple three dimensional puzzles overlapping each other, with missing pieces!

Jason 1979

The low pressure switch without any wires attached is closed, so good there. I don’t see any way to get probes down to the thermostatic switch, but it must be out.

i think what I am going to do for now is pull the connector off the thermostatic switch and jump the connector. Clean up the rest of the wiring and order a new thermostatic for replacement this winter.

I doubt the evaporator core will get below 33 in a Texas summer sitting 12 inches from the headers.

REELAV8R

In the schematic above it shows power to the solenoid as soon as AC is turned on.

And that the clutch is engaged once the pressure switch and the thermo switch are satisfied. Since the solenoid only needs to be energized if the clutch on the compressor is engaged you could simply splice in for power between the thermo switchand the clutch.
this way the idle solenoid is only activated if the clutch is activated.

the way the schematic reads it appears to me that the solenoid would still be active even if the thermo or pressure switch are not satisfied and de-activate the clutch. In this case that would leave you with a high idle due to continued power to the solenoid.

Jason 1979

Well I got all of the wiring sorted, cut to length, soldered,heat shrinked and covered in the split loom stuff. AC works now and at least the low pressure switch is connected again. Ran a wire from the light green over to the new Solenoid and that works as well.

Adjusted the solenoid so that idle speed is the same with or without the ac running.

I am am a happy camper for now. It looks like replacing the thermostatic is going to take u joints and a five year olds arms. It is way back in there.