1978?
If so, there's no low pressure switch and the system doesn't cycle. The compressor clutch is controlled by a thermostat and will run continuously until the evaporator approaches 32 degrees.

78 and 79 were like this. The cycling switch was added in 1980, I believe.

 

You could swap it over if you wanted. I did this on the 79 I have. Started having problems with the thermostat so I just bought the pressure switch had the wiring connector to fit it already and just connected that into the thermostat wiring harness plug. I did not cut any of the original harness. Been working great for going on 8 to 10 years now.

 

Thanks for the help guys, if it works on a thermostat, which is what I thought one of the pieces was I will leave it alone.

Next question what should my A/C gauges be reading?
Lo is 45~50 and Hi is reading 250is currently it is only about 92-95 outside but with my engine running the engine compartment is HOT.

Also how many speeds are there on the fan? It looks to be 4 position settings on the panel, but only 3 seem to work Lowest/Lo/Med/... and after taking apart the swithc, it was hard to tell, but it looked like a couple variable settings and a on/off setting.

The high setting or what looks like a high setting just shuts it off. Since the panel is really old and very little letters are left on it was hoping somebody could help out

 

Rule of thumb for the gauge readings is:
2.5 times the ambient temperature on the high side
26-30 on the low side (High blower, Max AC, windows closed, 1500 rpm).
You're pretty close on the high side. The low side will drop as the cabin temp drops.

The High setting on the fan is controlled by a relay out on the evaporator case. It's a metal can with 4-5 wires going to it. You can't miss it. One of the large wires goes to the blower motor IIRC. They fail fairly often.

 

Something like this?


If it is out would it still allow 3 of the 4 to function?

 

Just got off the phone with the Autozone HUB store, heading down in a bit to replace a bunch of the old electric parts. My thermostat switch/relay is missing the "coil" part and I can see where it use to connect to the bottom of the line before, might explain some things.

There are two green wires, light green and dark green anybody know where these go to, I am assuming the compressor originally? The compressor has two male spades one has it grounded to the bracket and it looks like the other was the dark green wire, but it is dead and the light green will provide 12v to engage the clutch.

 

The light green should be hot to the thermostat and when it closes the dark green should be hot to the compressor. The other should be grounded as you indicated at the compressor. The connector with both the light green and dark green should plug into the thermostat.

 

Well, now the fan works changed all the goodies out. Thanks for your help :You_Rock:

I will have to get a picture of the wire after I chase it down, it was cut near the compressor. The cycling thermostat does have the light green (2) and dark green (1) connector in tact. The dark green is providing the 12v to the compressor, but still have a rogue light green wire.