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Re: 3amp fuse keeps burning out
when a fuse blows, its telling you that theres a fault. this could be a loose or broken wire.
or alternatively, the fuse rating is too low. you could check the wires are tight. and also possibly try fitting a 5 amp fuse. check first that the fuse is rated correctly for the appliance. usually 3-5 or 13 Amps.
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You can take each thermostat wire off the control board and use a ohm meter and test to ground, should not have any resistance. Another way is turn off power take each wire off the board, then place one wire at back on the control board terminals ome at a time, untill the one you get to the one that blows the fuse. If the wires check out good sometimes the thermostat itself can have a internal short and cause the fuse to blow.
disconnect the thernostat wires from the control board. Put a jumper wire between R & G put door back on and turn on power. Blower motor
should run, if it blows the fuse then you have a direct short between R &
G at the board. Do this with R and W(heat) and R & Y(cool).
By disconnecting the thermostat wires and reinserting them make sure that they do not touch when inserted into each terminal. If it still blows
that little 3amp fuse when jumpering between each sequence as mentioned above, then I think your board is bad. When Jumpering out the Y terminal you will have to have the AC wires still hooked up. If it
blows the fuse in that sequence. Disconnect the wires out at the condensor.
Turn The Fan Switch at Thermostat to on, If nothing happens you need to check the fuse disconnect at
furnace if it is equipped with one, if not make sure
the breaker is not tripped.
If all of that is ok, make sure the blower door is secured, when it is secured it makes up a door switch which transfers all the power to the control
board of the furnace.
If you dont think its the blower door switch, remove the door and tape over the switch to simulate that it is closed. Check for 24 volts between R and C where
the thermostat wires go R is usually red and C is usually white. If you dont have 24volts at R and C
check to make sure that the little 3amp automotive
fuse is not blown, I think the fuse is purple and should easily be located on control board.
If the main fuse or breaker was blown or tripped, check to make sure the blower motor will turn by hand.
double check your wiring. R terminal on the furnace will provide 24 volts to the t-stat. W terminal in the t-stat will send 24 volts back to the furnace W terminal to turn on the heat. G terminal in the t-stat will send power to the G terminal in the furnace when the t-stat is switched to fan on. Y terminal in the t-stat will send power to the Y terminal in the furnace which in turn will send 24 volts to the A/C outside. The C terminal in the furnace should be connected to the c terminal in the A/C outside as well as to the T-stat. Check the fuse again