Could be compressor but much more likely an air leak in dump valves, spitter valve on air dryer, tank bleed valve, parking brake actuator, etc.. Need to find a chassis shop w/good working knowledge of air systems on diesel rigs or your will be spinning your wheels w/a lot of semi pro help at pro prices.
Here is a full education in the process. Old Forester had an intermittent problem that only got real bad when it was cold.
Perspicacity & stick-to-itiveness found a solution, hopefully armed w/a decent air schematic you can track down the problem in a whole lot less steps & a much reduced wad of sweaty money. Your problem should be easier to pinpoint as it sounds way more pervasive.