Why does the air suspension light come on?

Hi, My 91 TC does the same thing, I had to replace the compressor and dryer once, but I believe that it has something to do with the relay in the fuse box by the battery, it's the big square looking gizmo, use the label under the lid for the correct relay, I replaced one, and it seemed to help, but my light still comes on. I have found a aftermarket suspension system for these Town Cars. It is a set of heavy duty replacement springs, which replace the bags. I intend to buy them, they are under $200.00 not counting installation. Many reviews on these parts say the can barely tell the difference, and it eliminates the pump system completely, just how, I'm not sure. I have a friend with limos having same probs, says he will replace bags with springs for me as soon as I get $$$ for parts! I don't know if this will help, but good luck! Michael