Air Suspension problems

Hi, I know that this subject has been pretty well covered but I have a problem and need some help. My 98 Expeditions rear is sagging, badly. I dont get a check suspension light. The compressor never kicks on. I think that my air suspension sensor is bad. Where is it located and how can I tell if it is the compressor or the sensor? Thanks,
Hal

Hi, I know that this subject has been pretty well covered but I have a problem and need some help. My 98 Expeditions rear is sagging, badly. I dont get a check suspension light. The compressor never kicks on. I think that my air suspension sensor is bad. Where is it located and how can I tell if it is the compressor or the sensor? Thanks,
Hal
Hey I think that I know what your promblem is. This also happend to my Exp. if you look under the hood there will be the air compressor if you dissconnect the hose there will be an o ring that may be broken or just dry rotted replace that and it should pump back up.