My car is an 86 coupe.

So I installed the coolant bypass. In the process, I disconnected the two wire connector at the A/C compressor to make routing the hose easier. Everything's hooked back up, but now the A/C compressor won't kick on.The A/c wasworking fine prior to this, with plenty of freon.
How do I check to see if the compressor clutch is OK. I had another (non-vette)car once that, in order to check if the A/C clutch was OK, I hooked up the positive from the battery to the connector at the compressor. That car only had one wire going to the compressor. The vette's compressor is a two wire job, with a diode between the two wires (?).
How do I check to see if the compressor is OK. What is the voltage at the wires suppose to be when the A/C switch is on. BTW, when I turn on the A/C, the cabin fan comes on just fine. Another thing: the previous owner converted the car to R134, but that shouldn't make a difference with regards to the problem I'm having, as I think that it's an electrical issue.

Any ides?

Thanks,
Ed

 

First thing stick a multimeter into the compressor connector, and see if you got 12 V comin' in to it. (don't ground in the ground wire; rather the engine block)

Second, stick a multimeter onto your battery 12 V, and see if it will ground out on the ground wire leavin' the compressor connector.

 

I'm getting 12V from the green wire when the A/C is turned on. I will ground the connector to the battery + when I get home later.
What's confusing me is the two wire job going to the A/C compressor. One's green and the other's black. I'm guessing the black is (-) and the green is (+). If so, what's the deal with [what I assume is] the diode that sits between the black and green wires in the plug?

 

I'm not familiar with your model, is it a diode or a resistor? Don't understand it myself. The older style just ran battery voltage to the clutch coil, yes, green wire should be the hot one and the black should be ground.

 

Does your compressor have a pressure switch in the back? If so, it provides a gound for the clutch coil. It is a high pressure cut out switch.

 

Didn't the older style go from the battery, to the low pressure safety switch, THEN to the clutch compressor?

ATC: if this IS the case, then IF you do NOT get 12 volts at the green compressor input wire, then trace back the green wire to the switch at the [?] (orifice tube housing) - can't remember the name of that thingmobob[:@]
help?

 

Is the low pressure switch on the ground side of the compressor? Or the 12V side?

atc: If I'm wrong and mech is right, then you would have to do the test for ground capability differently...

 

So this is getting strange. I once again checked the voltage on the green wire (I touched the neg lead of the multimeter to the exhaust manifold). At first nothing, then 0.05V. So, out of curiousity, I checked the black wire (touching the neg multimeter lead to the exhaust manifold), it also showed a fluctuating 0.00V -0.05V.

I can't help but wonder whether, when I disconnected and reconnected the wire [during the aforementioned coolant bypass surgery], if I messed up the connector somehow. What is the function or the resistor/diode?
Also, where is the A/C relay? Maybe I should check that?
One last thing...it's47 degrees here. That doesn't perhaps have something to do with the compressor not kicking on, does it?

 

BTW, no pressure switch on the compressor that I can see...

 

Okay, we know the green is the power feed TO the compressor.

That 12 V comes either from the dashboard controller, or from the low pressure switch. Here's a pic of the low pressure switch on a '98 GM:

It's the electrical connector furthest away on the accumulator (silver thingmobob).

If 12 V TO the compressor comes FROM that accumulator switch, then one of the wires at the accumulator connector should have 12 V when the motor is runnin' , and the a/c is on.

IF one of the wires has 12 V with the motor runnin', a/c on, and power ain't gettin' to the compressor (like you say you got now), THEN you have no freon (turns off the switch), OR, you have a bad switch, OR, a short between the switch and the compressor, or you didn't test good - header should be rust free.

The other way it could be configured is like this:

12 V comes TO the compressor FROM the dash control (you say now you don't have 12 V, but we'll fake it). The ground wire FROM the compressor THEN goes to the accumulator switch, and then to the frame ground (if the 4 conditions above are good).

Simplified, it's like this: (the a/c relay is in-line there somewhere; mech probably knows. hopefully, it's in series; not parallel[&:]
12 V -> dash controller -> compressor -> accumulator pressure switch -> ground
or
12 V -> dash controller -> accumulator pressure switch -> compressor -> ground