my rear syspension wont raise up on my 2003 navigator
You have an air leak in one of the rear air bags and the system has seen a problem and shut them off.
Look for the airbag switch first. It will be in 1 of 2 places on that vehicle, either in the trunk with a little panel that snaps off of the left side and the switch is under it. Or it will be in the passenger front foot-rest area, you may have to stick your head up there with a small flashlight.
Also If you've had it serviced recently, the oil changed or anything, at a shop... Shops always disable the airbags when they lift a vehicle just in case the compressor kicks on and pumps the airbags full, thus blowing them out when you lower it to the ground.
bottle of "snoop~ https://www.google.com/search? q=snoop+for+leak+detection&source=lnms&tbm=isch&sa=X&ei=SpTMUum qLIOs2gW964DoBA&ved=0CAcQ_AUoAQ&biw=1152&bih=627
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