How To Know If the Air Conditioner's Fuse Is Blown? How to Test an AC Fuse - The AC fuses are one of the most crucial parts of your air conditioning system. You can better prepare for your cooling service needs and avoid expensive repairs in the future if you can figure out why your AC system is failing. Read on to learn how to identify whether an air conditioner's fuse has blown. Check out the lines that supply electrical power to the air conditioner. The value must be around 220 to 240 volts, indicating that the power source is working fine.