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My Coleman model 3400-823 electric furnace will not shut off. The blower and heating elements both remain on until I flip off the breakers. The thermostat's relay opens and closes in a normal fashion when the temperture is set above or below room temperature, but this has no effect on the furnace.

The furnace's fuses appear to be fine (multi-meter reads no resistance). The four limit switches also read zero resistance regardless of the thermostat's setting (above or below a normal shut-off temperature) - as checked with power off. I suspect either one of the limit switches or one of the two sequencers; but don't know how to narrow it down any further. Assistance would be appreciated.

Burt

Sequencer number 3120A3571

The sequencer controls the heaters and blower motor. The limit switches only act as a safety incase the heaters over heat. Usually the blower motor is defective when the over heating causes the limit to trip.

hvac1000

Thanks for the reply! Is there a way I can check with an Ohm meter to tell which sequencer needs to be replaced?

Burt

The sequencers come as a pair on a plate. Just replace both at the same time. With no voltage applied to any terminals ( remove wires first and keep track of where they came from)there should be no reading except at the bottom which is for the 24 volt coil to activate the sequencer. Sequencers are open unless activated by the 24 volt coil.

hvac1000