My 2002 Durango (200,000 miles) just suddenly- the ac compressor is knocking quite loud, It still cools but when a/c switch turned off and then the thermostat turned to heat still have the compressor knocking. Anybody have any ideas? Everything was just fine and then knocking. As soon as it stops raining (here in Fl) I am hooking up my guage to ac system to get reading. There was no issues at all and this noise and and ac compressor problem out of the blue. My wife has asthma and here in Florida in the summer time she has to have. I think I may have a problem with the ac clutch, but what would make the compressor kinda stay on when in heat? Any and all help is appreciated!!