Home ac condensing unit making loud noise. It seems to be after the system has run and turned off. Thought at first it was when the system was trying to run. Say bad capacitor not letting the compresor or fan run but when I push the contractor they run just fine with no noise. The system is pulling the contractor with no problems. So this had me keeping a better eye as to when it happens. Seems to be a bit after the system has finished running. It's quiet loud, far more then a contractor hum. I'm thinking its refrigerant some how changing pressure or something like that. It's enough to make the system vibrate. Not to long ago the air handler had the coil replaced. Iv read that techs sometimes over fill the system and this can cause a very loud sound when the system is running but this as I said happens when it's doing nothing.
Any help or direction would be so appreciate.