How to Replace the Fuses on a Central Air Conditioning Unit Your home is turning into a sweat box! It may just be that your overworked air conditioning unit blew a fuse. Here is how to replace the fuses on a central air conditioning unit so you can get back to what is really important--relaxing in your lounger with a tall, cool lemonade and chuckling as your neighbor is soaking wet, cutting his grass. Central air conditioner fuse 5 amp fuse in air handler blows The 5 watt fuse blows in the air handler. This only happens when the outside unit kicks on. The air handler will run if there is no power to the outside unit. Changed stat wires and it still blows the fuse. Answer: Sounds like you have a short between the outdoor unit and the control board on the air handler.