Dreaded Air Suspension!!!

[984x4]

I am still having problems with this piece of #$%* air suspension. Update:

The vehicle is a '98 4X4 Expedition, I replaced the compressor a little over a year ago, I have sprayed soapy water on the rear air springs checking for leaks, still haven't seen any leaks or cracks in the air bags.

The rear is sagging as I write this. This morning it actually raised up, then a few minutes later went back down and has stayed down all day. I spent a few hours checking air lines. I unplugged the relay under the passenger side headlight and the compressor cut off, plugged it back up and the compresor came back on. I then went to the next thing, followed the air line all the way to the frame rail under the driver's side door to a cylindrical valve of some sort. I disconnected the air lines to see if air was getting to the thing, and it was. On back farther, I can hear the solenoids on the air springs clicking and don't feel any leaks from the "Y" connector or air lines anywhere. I don't know what could be wrong with this thing, could a faulty ride height sensor at the rear be making it sag down?

Thanks for any help on this, just trying to save some money and do things myself, Ford wants $85.00 just to look at it, and another local shop wants $80.00, so I appreciate all the input I can get.