Well my #11 fuse in my 2007 f150 blew the other day. Put a new one in, instantly blew again. So I pulled the plug connector off the compressor, and with my voltmeter I'm getting continuity across the 2 pins on the connector. I don't think I should be?? Seems to me like I have a short somewhere.

I spent some time today trying to track it down. With the key in the on position, I can turn the ac **** to any position and the fuse will not blow. I can also operate the 4wd switch without blowing the fuse. The fuse ONLY blows when the truck is running and I turn the ac **** on. The fuse will not blow with the truck running and ac **** at the off position.

Any ideas?

 

Temps nearing 100 here with no ac is a killer!

 

Quick test:

Pull the A/C clutch connector.

Start the truck and turn to MAX A/C.

Does the fuse blow? If No, then the clutch winding is shorted. If yes, you need to get some schematics and begin troubleshooting the harness.

Clutch only engages when the truck is running - that's why the fuse won't blow in the KOEO state.

MGD

 

Just checked, fuse blew even with it unplugged. I'm getting continuity across the 2 pin plug for the clutch. Those 2 wires run up the front my engine and into the same wire loom my injectors and plugs wiring is run inside of.

Do you know where these 2 wires exit that massive loom of wires? If I knew where those wires exited that loom I could begin tracing a short. I really don't want to open up that monster ball of wires, asking for trouble there.

 

I guess its looking like I have a short between the plug at the clutch and a relay for the clutch that is activated when the vehicle is running. Since the fuse only pops when the vehicle is on.

I believe that relay is the one in the aux fuse box under the hood. If those 2 clutch plug wires run straight from the clutch to that relay in the aux box, I could try run 2 new wires to help eliminate where the short may be located.

I suppose its also possible for that relay to short, guess I could test that by pulling the relay and paperclip the 2 pins and see if the fuse pops.

 

Check the AC clutch diode to see if it's shorted. It and the clutch relay are in Aux relay box #1.

IF your truck is equipped with DRL, its relay appears to be the same. You can swap them relays.

 

Well I fixed it. Since it only blew the fuse when the truck was on, the short had to be after the relay which was located on the driver side fender wall in the engine bay . Since I had continuity across the plug that goes into the compressor clutch, somewhere in the wiring harness between the relay in the fuse box and the clutch plug the 2 wires were shorting. The positive wire that feeds voltage to the clutch when the ac relay is engaged by turning the vehicle and ac know on, is a gray wire with a white stripe. This gray wire runs straight from the clutch plug to the ac clutch relay which again is in the aux fuse box under the hood. Instead of tearing into my harness, I cut this wire at the plug and at the relay. With a few feet of wire I ran a new wire from the relay to the clutch plug, connecting them where I had cut them obviously. Works great now! $5 fix and cold air so I'm happy