Twinboat is right.
In my former life in the Middle East we had dozens of roof and window AC units and did repair them on a regular basis. But, we had nothing but time and no new ones to be had. In the real world, all you can do is make sure it's clean and replace if required.
Dennis & Carol
2003, 4006, 41' DutchStar, [SIGPIC][/SIGPIC] Spartan, ISC 8.3L W/BanksPower - 2013 Honda CRV, BlueOx Baseplate, Aventa Bar & Patriot Brake. And the 04 Bird, Sunshine Car.