Intertherm M2RC 100A-16BN furnance does not turn on.

[slooowr6]

Hi,
Need some help trouble shooting before I order the 903106 control board. Here are the symptoms.

1) The furnace blower does run if I switch the thermostat to "Fan".
2) If I turn off the thermostat and powers up the furnace the red LED on the control flash once repeatedly. Read the fault code it said "Limit Circuit Open or External Load On "W"". I use multimeter verified the circuit goes through the limit switches is in fact closed.
3) If I turn on the thermostat and turn up the temperature. I can hear a click but immediately the small 3A fuse blown.

Do I have a blown control board?

Thanks for any tip you can spare!

Alex

[Robert]

Hi Alex,

Disconnect wire from W on t-stat and W on control board. get a new length of wire and connect to both W's.

Power up WITH new fuse and see if it still blows.


Thanks,
Robert

[slooowr6]

Robert,
Thanks for the tip.
I ran a new wire from W on t-stat to W on the board. The on the furnace, the moment t-stat ask for heat the fuse blows.

Alex

[Robert]

Hi,

Turn power off, disconnect wires from t-stat W and RH and tie together.

Turn power on and see if fuse blows.


Thanks,
Robert

[slooowr6]

Just to confirm. Disconnect the wire from t-stat and jump W and R terminal on the control board?

Thx
Alex

[Robert]

Either way is fine.



Thanks,
Robert