I HAVE A MODEL 921.166420 AIR COMPRESSOR. WHEN TURNED ON MOTOR RUNS FINE, SOON IT BOOGS DOWN, AND THROWS THE RESET BUTTON ON THE MOTOR. I UNHOOKED THE AIRLINES LEADING TO THE PRESSURE SWITCH AND MOTOR RAN FINE AND PUMPED AIR THRU THE OPEN LINE. OS THERE AN ADJUSTMENT ON THE PRESSURE SWITCH,I HAVE SCREWED THE PLASTIC SCREW IN AND OUT, IT DOES NOT MAKE ANY DIFFERENCE.