Auto leveling problem, car is jacked up!

I have a '99 Silhouette my air shocks in the rear are maxed out and won't come down. I have been following the troubleshooting instructions on this forum and have determined my "Auto leveling sensor" or "ALC compressor head is bad". Any suggestions on how to replace the air compressor head?
Thanks for help or suggestions.

look at the rear axle from the rear of the van and you may see the leveling arm (sensor) arm or ass. may have come undone or broke loose causing the van to max out on the ride hight.

Thanks for your reply. I have found the sensor, and it seems to be OK. I took it off and manually pushed it in to the "low" position, and the compressor kicked on. While it is in the "high" position it doesn't seem to do anything. That's why I believe it is the solenoid on the top of the compressor that is not working.

Sounds more like a bad leveling sensor...

yeah the solinoid lets air out. have also seen the switch on the airpump in the panel left on . g.m. in their wisdom put the soliniod behind the rear tire and faced the wiring harness up with a cheap seal on top and because of this the soliniod doesn't last too long.the soliniod vibrates to let off ecxess air and if its gunked up inside or shorted out it can't release the air.i took mine apart and found a rusty mess inside.have to give it to them engineers"at a boy dumb ***". the soliniod is on top of the pump.i think i priced a compressor head at $140.00 at dealer.