A/C Compressor Wiring

[Chevelle_Nut]

My 69's compressor won't engage all of the time. If I give the clutch a 12 volt direct connect it will come on but from the dash it will not. I replaced the plunger switch, after replacement it engaged a couple of times but quit again. The green wire runs to the compressor from the switch, is there a junction or relay between the switch and compressor? The wiring diagrams online do not include the A/C circuit. Does anyone have any wiring diagram for a 69 they can post or link to? Thanks in advance

[Hank70SS]

No AC on my car so I can't say for sure. Not sure when they started using them but AC systems typically have a pressure switch somewhere. If there is no charge in the system, all the freon has leaked out, the pressure switch opens and the compressor won't go on. Keeps the compressor from burning up from running dry. Check the AC plumbing, receiver/dryer, etc to see if there is a switch in it somewhere. Could be a bad switch or low freon level.

[Chevelle_Nut]

The freon is full, if I jump the compressor over using a 12 volt wire from the batt to the terminal on the compressor it will freeze your tail off. The 69 does not have a superheat switch like a 72 does.

[Hank70SS]

Isn't there a relay on the firewall somewhere? I'm trying to remember, I've seen some of the wiring for the AC circuit but don't recall the details.

[Chevelle_Nut]

I just came back in, the ambient sensor on the evaporator housing is in line between the control head and compressor, I ohm ed it it and the wire is good from the compressor to the ambient. I jumped the ambient and still no luck. I am going to do more wire tracing a little later.

[Chevelle_Nut]

Here is what I found, on a 69 everything feeds back to the blower switch, it acts a power distribution junction. I am gong to try to repair the switch first before replacing it.