I just got done replacing my air suspension (LLS) compressor, for my 2000 Expedition 4WD, and wanted to summarize a few things about the process. My "symptom" was pretty obvious - the rear end dropped, so that it was resting on its bump stops (took a couple of days for it to drop totally) and the air compressor wasn't running at all. I looked at the signal coming in at the compressor relay (mounted in the front right wheel well, in front of the wheel, and sort of behind the headlight. I saw evidence of a signal being sent to the relay on pins C and D (Measured something like 7-8 volts across these pins, which went to less than a volt when the suspension control module was trying to tell the compressor to run.) But, the relay wasn't turning on. I jumpered pins A+B together at the connector, which provides a direct 12V to the compressor. But still the compressor wasn't running. My conclusion was that the compressor was bad, but that the relay was also probably bad (possibly burned out as a result of the failed compressor).

I ordered a rebuilt compressor from American Air Suspension (www.americanairsuspension.com), for something like $155 plus shipping, which is less than half of what the dealer wanted for a new one. There are several companies selling these, for similar prices. I more or less picked AAS at random, but liked the trouble-shooting info they had on their web site. They also offer a 2-year warranty, versus the more typical 1-year. I also ordered a replacement air line union, as a "just in case" part. My experience with them was very positive. The initial processing of my order was delayed for a few days by the fact that one of AAS's suppliers (I am guessing for the air line union part) was impacted by recent hurricane rain/flooding in Florida (AAS themselves are in Tennessee). But to make up for the lost time, AAS priority-mailed my parts, at their extra expense, so they got to me on schedule. (In time for doing the work over Labor Day weekend.)

The relay seems to be (more or less) only available from Ford, so I paid almost as much for it as for the compressor, although my dealer did give me a discount on it.

The new parts went in fine. The rebuilt compressor came with a rebuilt dryer, new rubber noise/vibration isolators, etc., but you still need to transfer it to the mounting bracket that the old compressor/dryer unit is mounted to. My tips for installation are:

- remove the battery, and remove the whole battery tray (4 bolts)
- this gives enough room to unbolt the washer reservoir, which can then be moved to the side (without disconnecting the fluid lines, nor its electrical connector(s).)
- remove the electrical connector. Ford electrical connectors are prone to having their plastic locking tabs crack when you remove them, but in this case the tab that may crack off is on the side that you are replacing, anyway.
- remove the two air lines (or one line, for a 2WD). Push in on the orange collar, while pulling out on the line.
- remove the three bolts holding the compressor/dryer assembly, and remove.
- remove the old compressor/dryer from its bracket, and mount the new one. Pay attention to what side the bracket is mounted to, before you take the old one apart.
- my new assembly didn't come with the orange plastic collars on the dryer's brass air-line collets. These aren't really essential, but what I did was gently pry the orange plastic collars off of the old dryer, and then they just push onto the new dryer.
- basically reverse the above process to install. When re-inserting the air lines, push them in as far as they will go, and then gently pry or pull back on the orange collars. The air lines should then stay in place even if you tug on them.

In case my relay wasn't actually bad, I tried using the old relay with the new compressor, but it was clear that I wasn't getting 12v through the old relay. So in my case both the compressor and the relay had been bad - probably due to the bad compressor drawing too much current through the relay, and frying the contacts.

After this, my suspension was back to normal. I was holding my breath a bit, when I first started the car, because it took several cycles of the air compressor running for the rear suspension to pump itself up fully. The new compressor runs MUCH quieter than the old one. Actually, Ford has for some time sold a kit to reduce the noise/vibration of the compressor, and I had put in this kit a few years ago (basically it consists of a new bracket, with new rubber isolators). And that kit had made my old compressor somewhat quieter. But this new compressor is VERY quiet - I have hard time even hearing it run. Some of that may be due to the fact that it came with new rubber isolators. But the compressor itself seems very quiet.

 

Good write up!

Eddie is the man at AAS. He has helped many times with my Lincoln Mark and Ford Exp.

 

If your old isolator rubbers are still in good shape, can I interest you with a swap on used but working level sensor? I'm in CT 06110. PM me if so.