Warranty call. Per Ruud factory rep. I replaced the high pressure switch, installed a new defrost circuit board and changed the filter drier. Pressure tested braze joints with nitrogen. Pulled a vacuum and weighed in factory charge of r410a refrigerant, then charged system to proper subcooling. Injected ac renew into refrigerant system. The unit made the noise once and hasnâ€™t made it again. System and defrost operation is significantly quieter. Told client the system will need 24-48 hours for the ac renew to properly circulate throughout the entire refrigerant system.