I have a rheem classic 90 plus heating and air unit. It kept blowing the 3a fuse immediately when attempting to start; so I replaced it with a 5a fuse. Now it will run for about 60 secs, shut off, start again and keep repeating that cycle.

Check all low voltage wiring for damage/shorting out. Usually something in the low voltage wiring or controls cause the fuse to blow. Check the wires going to the outside unit especially from the house to the unit itself. Sometimes a dog or other animal will chew on them.

The unit is inside my home and the wires appear to be fine. The 5a fuse is not blowing but after 60 sec of running, it starts turning off and on every sec. when I turn it to heat or fan it works. Only the ac does this.