AC repairs: The real reasons behind blown AC fuses May 18, 2016A fuse is a metal filament or wire, usually in some type of casing. It’s located in the disconnect box, connected to your AC. It is there to protect your machine, to Central air conditioner fuse The fuse box should be in the line of vision; it should be within REACH from the condenser unit location. The fuse for HVAC unit is Heavy duty time delay cartridge fuses. The fuse is within the fuses holder. The within REACH disconnect is in metal box.