Well the butt end of my mom's '02 expedition dropped to the bump stops the other day and my dad and I have been trying to get this thing figured out. It's a 4x4 Eddie Bauer w/ 5.4L and 4 wheel LLS with 72,000 miles on the odometer.

First off we thought it was the compressor, so after replacing it we hooked the old one up directly to the battery and it fired right up, so strike one.

Then we pulled the relay and I check for power to the plug on the big wires. Jumped between A & B points and the compressor turns on. With the key on engine off there is 11.9 V between A & B and 5.9 V between C & D. I hooked C & D directly to the battery to see if I could hear the relay click on and off, no luck. So there for I assumed the relay was dead because from what I have read I understand that the when the compressor starts to wear out it draws more amps which fries the relay.

So went to for Ford and got a new relay. Bolted it up and plugged it in, start up the expo and the compressor still doesn't kick on.

I went ahead and jumped the wires between A & B again to see if the rear would go ahead and air up. With key on engine off the compressor comes on but doesn't air up the rear. While laying under the front bumper after turning off the compressor which ran for about 30-45 sec I heard a slight hissing sound. Sounds like a pin hole size air leak in an air line. I sounded to be coming from somewhere around the AC compressor.

So anybody have any ideas what my problem is? I don't really know where to go from here. Also all fuses check to be good under the hood and in the cab and the Air Ride switch on passenger side kick panel is in ON position and the check suspension light on the dash has never been on.

 

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First thing to do is to track down the air line leak. The new relay could be bad. There is a way to test it with a voltmeter; you would have to search old posts to find out how. I had similar problem and after pulling off the relay plug so many times that the plug connection got loose. Also, make sure all four doors are closed to activate the air system...you should hear a click, click sound in the back when the solenoids above the bags open and close, which is a part of the testing process I believe. If you fix the air leak and have all doors closed and hear the clicking noise in the rear you can jumper the relay plug to get the rear to fill then turn off the system and make sure there is no other leaks.

 

Have you disconnected the batter and reset the system? You do need to find the air leak and fix it. One common place for an air leak is at the union that provided air to the rear bags. It is located under the hood near the master cylinder.

If this is not the source of the leak, then you need to jump the compressor and let it run for brief intervals while using a soapy water solution to find the leak

 

Bambiblaster, I am traveling the same road as you and have done the same as you and hearing the same as you. I will go and do as they have suggested. Did you fix your problem? Keep me posted and others, too, of course. My first post here and it just happens to be in a thread that I can absolutely relate to.