'67 compressor not getting juice

[William F.]

My '67 factory AC compressor is not coming on when I pull the "AC" knob. Compressor's not frozen just not engaging. Fuse OK.
1. Where to check no voltage problem? Hope it's not switch associate with "pull AV' knob. Understand very difficult to get to. Isn't there a second switch on top of heater box- not talking about the one that directs hot H2O to heater?
2. If I want to "hot wire it on so AC will be on when key is on, where from- horn relay hot side? Or is there a source on same side of engine compartment as AC? I see a couple of connectors coming out of wiring harness just above blower motor that aren't connected and appear to be "extra" nonused connectors (unless they're supposed to connect to something, but don't see where)
Thanks

[Michael H.]

Re: '67 compressor not getting juice

Isn't there a ground wire by your compressor ? Could be bad clutch on compressor.

Mike

[Larry M.]

Re: '67 compressor not getting juice

Bill:

There is a simple switch atop the heater box that supplies 12 volt power to the AC compressor clutch when you pull the AC knob. The cable attached to that knob activates the switch and also moves a door inside the heater/AC box as well.

I would disconnect the 2-wire connector at the AC compressor, pull the AC knob and see if you get 12 volt at this connector. It has 2 wires, one should be 12 volt (green) and the other is ground (black).

If you don't get 12 volts at the compressor, this switch is probably bad. The good news is they are still available from Ebay and LICS. It is possible that the incoming power wire to this switch is loose/broken. So you need to troubleshoot and check.

I guess in a pinch, you could run a 12 volt jumper to the compressor clutch, also provide a ground wire, and run the compressor all the time. But not a good idea long term. I might do this if I was far from home and my tools, it was hot outside, and the wife/girlfriend wanted the AC on.

Larry

[William F.]

Re: '67 compressor not getting juice

Thanks, Larry. Yes, after I sent the initial post, I looked things up in the CSM and it's set up just as you say. I'll check for voltage as you suggest. If no voltage at compressor, one more possible cause for problem would seem to be that maybe the cable from the "Pull AC" knob may need adjustment at the switch on heater box to close contacts as it should. If I have to pull glove box to check switch/cable, can I disconnect clip to glove box light or do I need to cut it and reconnect with small plug on wire? Seems like some threads say hard to get that clip back on lamp.
Don't guess could be a problem with pins in notorious firewall connector that goes to AC could it? Everything else electrical works.

[Larry M.]

Re: '67 compressor not getting juice

Bill:

According to the wiring schematics, this wire does NOT go thru the infamous firewall connectors.

Larry

[Edward J.]

Re: '67 compressor not getting juice

Bill, Not sure if 67 uses a thermal limiter as my 72 does, but its a fuse of sorts, when the system run low on Freon charge it keep from burning the compressor out but opening the circuit to clutch. Larry may know, I do not have the diagram for your year.

[Larry M.]

Re: '67 compressor not getting juice

Bill, Not sure if 67 uses a thermal limiter as my 72 does, but its a fuse of sorts, when the system run low on Freon charge it keep from burning the compressor out but opening the circuit to clutch. Larry may know, I do not have the diagram for your year.

Not originally used by GM for 1967 cars. This came a few years later. Someone might had added one at one time, so I agree Bill should look for it......just in case. But I would not expect it to be there. Just a 2-wire connector to the compressor clutch at around 10:00 o'clock position.

Larry

[William F.]

Re: '67 compressor not getting juice

Feel problem is in area of the AC switch mounted on heater box since when I pull the AC on knob, the low speed blower which is supposed to come on when AC is on doesn't come on as well as compressor not coming on.
Fuse in fuse block looks OK but will substitute a new one just to be sure. Yes, Compressor ground wire is connected.
If not fuse, guess I'll remove glove box and check cable to switch and switch itself.
How about best way to disconnect glove box lamp when removing glove box as a unit-remove clip to lamp or cut then reconnect wire?
Thanks

[Keith B.]

Re: '67 compressor not getting juice

did you check the 30 AMP inline fuse about six inches from the horn relay? the fuse in the fuse block under heater is a 25 amp fuse

[William F.]

Re: '67 compressor not getting juice

Turns out I had the cart before the horse. After checking electrical connections to compressor with volt meter and observing compressor clutch in on and off positions, clutch IS getting full voltage and clutch is working. BUT, nothing moving in sight glass-no bubbles either, appears full of R12 and no change in temp of either compressor hose. My excuse for thinking problem with clutch is that there's no drop in engine rpm with clutch engaged and no sounds from compressor. Are internals of my original compressor shot or should I add some R12 and see what happens?
Thanks in advance
Sorry for original misdiagnosis and unnecessary questions

[Domenic T.]

Re: '67 compressor not getting juice

William,
You might try this. The A6 is a tough compressor and internally oiled if it has oil in the pan. Make sure the gas is out, remove the manifold at the back of the compressor and put a finger on each port. Turn the clutch hub (not pulley) by hand and see if you can feel it suck or blow. All this is done with engine & power off. If you can feel or hear air movement, you most likely have a working compressor. Then look for oil around the hub area and all the fittings to see why the gas has leaked out.

Dom

[Larry M.]

Re: '67 compressor not getting juice

William,
You might try this. The A6 is a tough compressor and internally oiled if it has oil in the pan. Make sure the gas is out, remove the manifold at the back of the compressor and put a finger on each port. Turn the clutch hub (not pulley) by hand and see if you can feel it suck or blow. All this is done with engine & power off. If you can feel or hear air movement, you most likely have a working compressor. Then look for oil around the hub area and all the fittings to see why the gas has leaked out.

Dom

Good advice from Dom. However, I would first do two things:

1. Energize the clutch briefly with the engine running and see if the compressor shaft moves. The clutch is always turning on its bearing, but the compressor shaft is still/stationary until the clutch "makes up".

2. Either hookup a set of gages to see what the system pressure is, or if you don't have them, use a thin pencil or wood dowel or blunted nail to push down on the Schrader valves and see if you have any refrigerant left in the system. It should be at around 80 psig at normal outside temperature in the summer and should blow out pretty strong if the system is fully charged.

If you lost all the refrigerant in the system you will need to re-pressurize the system and find the leak using a soap solution or a refrigerant electronic leak detector............or find a mechanic that can do it for you. If you have a compressor issue, Dom is the best in the business.

Larry

[Jim T.]

Re: '67 compressor not getting juice

Seeing nothing when looking at the sight glass when the compressor is running seems to be a complete loss of R12. Should be able to detect movement of R12 from the sight glass.