No A/C in the summer heat...

[Parentnoia]

I just checked and I didnt see a difference between button engaged and unengaged.

 

[great white]

Couple causes:

Low pressure (needs recharge after leak that cause low press is fixed)

Pressure switch faulty

Bad control head

Bad clutch coil

You can jump the switch to find out if the Clutch engages, but that's only to verify the clutch coil is good. Only run it a few seconds like this as the compressor can be damaged if pressure is low (IE: no lubrication).

If you don't have gauges, you can't check the pressure so it's off to the shop for this.

You can change the switch on spec, but I'll bet you have a leak and that would just be wasted money.

If it has the original GM compressor, you most likely have what is infamous in auto AC circles: "the belly leaker".

These are known to fail in the middle joint on the compressor housing and the seal allows the refrigerant to escape. What happens is the aluminum corrodes over the years and since there is a joint right in the middle of the housing it migrates under the joint O ring seal and allows the refrigerant to escape.

Unfortunately, replacement is the only cure....and only a shop is going to have the equipment needed to pull the vacuum on it and pressurize it again...

 

[Parentnoia]

[BIG UPDATE]

Okay, big update.

Bit the bullet and bought a can of that AC PRO stuff and emptied the can into the engine.
First off, easy to use.

Second, it semi fixed my issue. The clutch now engages. But it engages, disengages, engages, disengages, etc.

Should I buy another can since it may be empty and the specs say it needs about 3 cans worth of R134a. My thinking is that, with the fact that I did not know that switch on = engaged, whether the fan is on or not, I could have just run it dry from always being on.
On the pressure gauge on the hose, I have good pressure until the clutch engages and it drops, and the clutch disengages. I'm guessing that's because it doesnt have enough pressure to stay on?

 

[SAATR]

Right, there isn't enough refrigerant in the system to maintain adequate low side pressure, so once it drops below the threshold pressure it disengages the clutch until the pressure equalizes across the orifice tube and the system sees enough pressure to engage again. The other possibility is a system restriction like a plugged orifice tube, but isn't as likely. You really need to see what the high side is doing to properly gauge the health and function of the system, but given your circumstances, I would say add another can of R134a and see where it gets you. You really need to run down your leak so you don't waste money on refrigerant. I would also suggest a set of gauges so that you can just buy straight R134a instead of the marketing price premium that you pay with AC Pro. R134a is R134a, no matter who makes it.

 

[great white]

Okay, big update.

Bit the bullet and bought a can of that AC PRO stuff and emptied the can into the engine.
First off, easy to use.

Second, it semi fixed my issue. The clutch now engages. But it engages, disengages, engages, disengages, etc.

Should I buy another can since it may be empty and the specs say it needs about 3 cans worth of R134a. My thinking is that, with the fact that I did not know that switch on = engaged, whether the fan is on or not, I could have just run it dry from always being on.
On the pressure gauge on the hose, I have good pressure until the clutch engages and it drops, and the clutch disengages. I'm guessing that's because it doesnt have enough pressure to stay on?

That's short cycling.

Typically, low pressure.

Problem with dumping more refrigerant in there without finding out where the first batch leaked out is you'll be right back where you started in very short order...

 

[Parentnoia]

Oh, well the AC Pro came with a reusable hose, so I have one for other R134a. Already bought a second can for $10 and put it in. Had AC for about 2 hours (that's all a drove before parking for the night). Next morning, cranked up the AC, and nothing. No clutch engagement. I havent put the gauge on it yet since then. Sorta admitted defeat.

 

[great white]

Yep, that would be a leak...And A gooder.