My coleman 13,500 roof a/c year 2000 does not blow

My coleman 13,500 roof a/c year 2000 does not blow as cold as used to. I have cleaned the top condenser coils, with no help. It also at times will seem to pull a heavy load when I assume the compressor kicks in, very heavy that the generator bogs way down, then runs free, i believe the compressor is shutting down as cooling worsens, it was 85 outside and the coach continued to get warmer. The AC unit has shut down completely before, not sure why I waited 30 minutes and it restarted.