Why does the fuse in air conditioning unit keep blowing?

Question

The other day i noticed my thermostat shut off....Went and checked inside the air unit in basement and a 5 amp fuse was blown...Replaced fuse and it blew again...I can run the fan only on thermostat and fuse wont blow...I switch over to auto and cool and fuse blows...The air conditioner compressor outside wont even come on before the 5 amp fuse blows....It is a Trane....At first the fuse took about 3-4 minutes before it would blow...now its immediately....When fuse blows thermostat stops working completely....

Answer 1

I'll go with RG on this one.  As others have said- there is a short.  The HVAC unit is 220 v which you do not want to mess with.  Get a pro HVAC guy or gal out and stay with them to see in fact what the prob is/was.

Answer 2

Most are on the right track, a shorted low voltage wire or component. If you dont see any obvious shorts in the low voltage wire to the outdoor unit, call a service tech. Could also be a bad contactor coil.  

Answer 3

I would have an AC service tech check it out. It could be the motor in the condenser that is causing your fuse to blow.When the motor goes it will draw to many amps and that will blow your fuse.

Answer 4

This fuse is for the low volt system 24 volts, the low volt wire outside near the condenser must be damaged and in need of repair go look around and see if you find bare wires! The low volt wires are very thin and in most cases have a brown cover on them, they can be damaged by weed eaters or hedge clippers. Sometimes this wire runs up a metal cover outside of the home and if not blocked off at the bottom mice can get up the cover and chew on the low volt wires. 95% of the time the problem is outside near the condenser. If you find bare wires pull them apart from each other and do  not let them touch, this is what is causing the fuse to blow, put tape on them to insulate them.

Answer 5

My first thought would be to check the wiring going from the furnace to the condenser (outdoor unit). If these wires are shorted, or touching each other it could do what you have described.