rear air suspension stuck up

My friend has a 94 DeVille Concours and the air suspension in the rear is way too high. The compressor still kicks on for a couple seconds when you first start the car, but the air does not vent from the rear. What do I have to do to get the air to vent from the rear air suspension? I checked the height sensors on both control arms and they are all connected and look fine. Any help would be great. Thanks a lot.

I can't believe that out of the 70 people who looked at my post doesn't know how to vent the air out of the air suspension in the rear of the Caddy. My old Lincoln simply had a pressure release valve on the compressor but the Caddy doesn't. On my old 1992 DeVille you simple just adjusted the height sensor. I mean there is already a blown strut on the Caddy from the suspension being so high. Someone please help.

The simple purchase or access to a shop manual would have answered this question, not every issue on every car can be answered off hand over the internet! The relief valve in the compressor is stuck or the level sensor is bad, satisfied? Remove the line from compressor to exhaust the system temporarily.