I've got an 89 350 supercrew and the ac isn't working. I traced the wires as far back as I could and getting no voltage before it goes into a hard to trace bundle. I am in need mainly of a wiring diagram so I can find more spots to test. Or if there any common component failures in this system, I'd like to know their locations.

I'm trying avoid buying a pressure gauge set yet because it has one r12 and one 134a fitting, but I'll be doing a gull 134a swap down the road, but I currently have no garage and tools are in storage for next 3 months.

Thanks in advance

 

If you have one 134a fitting already, then its been converted already.
Most kits don't come with a high pressure fitting for 134a. Just the low side fitting.
For your AC not to work, I'd bet its the pressure switch. Under hood, pass side, its a little elec switch on the round black thing by heater box.

Turn AC on high, then take a little jumper wire and bypass the switch. If your pump comes on, either the system is low on refrigerant, or the switch is bad.
The switch can be replaced without draining the system. It's screwed onto a schrader valve.

 

Thanks ill check that. It's definitely r12, it's a Frankentruck with a 12v cummins but all the wiring up to the compressor is from the ford. It had a bad fitting on the previous owner and he could only get ahold of the 134 high side. Is that the only switch in this system? Because I've already jumped it b+ to the wire before it goes into the bundle and it kicks on

 

You jumped what to b+.... The compressor.

There is a pressure safety switch that needs to be bypassed, not battery power put to it.
It is the primary switch for turning the compressor on and off.
It's near the heater box on the side of a tank. Sometimes there's another switch in a hose/line but that does nothing as far as I know. (Kinda like the pressure switch in the ps hose)

 

If thats the only switch, thats what I did effectively. I found a wiring diagram at my library. I'll post what my diagnosis is. just over a much larger area (so I could have also found an open in the process.)