1996 Lincoln Continental suspension air bag

Its hard to say without seeing and listening to it myself, but "BOTH" air springs are the exact same age and this is the reason why they should be replaced in pairs.

The different sounding compressor could be that the compressor isn't straining anymore. In other words, it "may" not be making any pressure anymore -OR- theres a major leak and the compressor is just blowing air into the atmosphere.

Unless your handy, you may want to have this looked at by a professional.