Outside AC Unit Won't Turn On? What to Do Before Calling Apr 15, 2015Your main electrical panel — On old homes this is a ‘fuse box’ while newer homes have a circuit panel. If it’s a fuse box, look for a blown fuse (replace that thing!) On a circuit breaker, look for a tripped circuit and flip it to “off” and then back to “on”. At the shutoff box near the AC — Some models of air conditionersAir Conditioning · Repair & Maintenance AC repairs: The real reasons behind blown AC fuses May 18, 2016This could be because of too-high levels of refrigerant in the AC, or as a result of frequently turning the machine off and then back on very quickly (within a minute of turning it off). Wear and Tear on the Fuse; The lifespan of a fuse can be up to 20 years. AC fuses are usually what is known as ‘slo-blow’ or ‘time delay’ fuses.