Testing Electric Furnace Sequencers

Turn off power to your furnace at the circuit breaker. Access the sequencer by removing the front panel from the furnace. Look at the furnace schematics for an outline of where each part is in your furnace so that you can quickly identify the sequencer. The sequencer will have wires connecting into it and several metal tabs on it.

Remove each wire. Do not pull on the wire itself; disconnect it at the terminal base.

Test each set of terminals for continuity by using a multimeter. Turn the multimeter to the Ohms of resistance setting. The bottom terminal is called the bi-metal heater terminal and should have continuity. Touch one terminal with the black multimeter probe and the other terminal with the red probe. If you see a “1” appear on your multimeter, it indicates that the terminals do not have continuity and the sequencer is bad.

Look at the metal tabs on the sequencer; these are also terminals. A label will appear under each. Test each pair for continuity. For example, to test the M1 and M2 terminals, touch the black probe on the M1 terminal and the red probe on the M2 terminal or vice versa. You should see an infinity reading on your multimeter for each set of terminals. If you do not, the sequencer is bad and should be replaced.

Turn the multimeter to measure more than 220 AC voltage. Power on the furnace. Test each terminal set for voltage. If you read any kind of voltage on either set of terminals, test each one again after three minutes. If you still get a voltage reading, the sequencer is bad and needs replaced. You should get no voltage reading after three minutes.