空調突然不工作了有多種原因。我會按以下步驟檢查。

AC compressor clutch whether engage. 

If it does not engage, it could be the relay, low freon or bad clutch.

If it does engage, then it is not the relay or cluth.  Then it could be low freon, bad compressor or expension valve.

No matter what, the best way to check the AC problem is to use AC manifold gauge to check the low and hi end pressures.  It will point to the problem.  It only cost $50 to get the gauge from Harbor Freight.