Ford Expedition rear air suspension compressor

I have a 1997 Ford Expedition with the rear to the ground. I have replaced the air compressor 2 times now and have left it in the off position about 2 months ago. I live in New England and its very cold. I just recently turned the switch on for a better ride, but the back end has dropped and the compressor has not come on. I have tried jacking up the body in the rear, banging on the unit.(Ford tried this once and it worked), I have tried to reset the switch by factory instructions. At this point, I do need this fixed, but also am wondering if I can inject air into the lines or the suspension system somewhere. At least for a temp fix. Then I would shut off the switch again if I could get air back in there. Please help!