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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Every time i turn thermostat to heat it blows fuse in unit

Customer Question

every time i turn thermostat to heat it blows fuse in bryant unit
Submitted: 1 year ago.
Category: HVAC
Expert:  Kcrand36 replied 1 year ago.

good evening, I am Kevin from Ja.......

can I get the model # ***** your furnace?

Customer: replied 1 year ago.
Expert:  Kcrand36 replied 1 year ago.

do you have a heat pump or electric heat?

Customer: replied 1 year ago.
electric heat
Customer: replied 1 year ago.
its the 3 amp inline fuse on the red wire thats hooke to the thermostat wires
Customer: replied 1 year ago.
as soon as the thermostat clicks by either turning the switch to heat with the desired heat setting set above room temperature or by raising the desired heat it blows
Expert:  Kcrand36 replied 1 year ago.

you could have a defective contactor or relay. the coil could be shorted causing the blown fuse.

Customer: replied 1 year ago.
how can i trouble shoot that?
Expert:  Kcrand36 replied 1 year ago.

first thing I would do is shut off power to electric heat, pull both wires off coil and check the coil with ohm meter from coil to ground, if you have any continuity, replace the contactor.

Customer: replied 1 year ago.
My mistake on the electric heat or heat pump. It's a heat pump. Can incorrect fan settings on the thermostat blow the fuse link in the red wire?
Customer: replied 1 year ago.
Could a bad thermostat cause the fuse to blow?
Expert:  Kcrand36 replied 1 year ago.

I know this is probably NOT what you want to do, but try it on AC, It could be the contactor out in the condensing unit for the compressor. If it works in AC, that is probably not the case.