I have voltage at the main fuse panel under the hood. The relay fuse is good and the relay is good.

I ran 12 volts directly from the battery to the Compressor and it engaged.

There is no voltage at the plug that plugs into the compressor so I am assuming there is a problem in the wire loom between the fuse panel under the hood and the plug on the end of the line. There is a diode, or two (?) in the lines coming out of the harness and to the plug. Do you think the diode(s) is fried or do you think it is something else? If it is the diode, or diodes, are these dealer only parts or can I go to any radio supply shop?

Thanks for helping a Ford Newbie.

 

Are you sure the system is charged? If the system is low on freon the low pressure switch will not allow the AC relay to engage and no power can get to the compressor.

You can easily check this by pulling the low pressure switch plug and insert a jumper between the terminals. If the compressor engages have the system check for low freon.

 

Ah Hah! I'm not sure of that at all.

I did not know there was such a switch. I will have it charged tomorrow.

 

Its on the passengers side AC line coming from the receiver/dryer (black metal cylinder in front of the AC box).

 

All you have to do is unplug the switch and cross it with a wire and see if it kicks on. If so the system is probably low. Mine wouldn't do that either so I kept working with it till I found I have a relay that had bad contacts inside. Works great now.