The sequencer on an electric furnace is a switch mechanism that activates the different heating elements inside the unit. A sequencer is essential for proper furnace operation, because if all the elements were heated simultaneously, the demand for electricity would pop a fuse or trip the circuit breaker. If the furnace is not heating normally, or if you can see that some elements are glowing orange but not others, the sequencer may be defective. A simple circuit test using a multimeter will let you determine in less than a minute whether the part is broken.
Things You'll Need
Shut off the electric furnace at the circuit breaker, or remove the fuse for the circuit in the fuse box.
Extract the screws in the service panel on the side of the furnace to take off the panel and locate the sequencer. It's at the top, connected to several pairs of wires. Each wire pair attaches to a heating element inside the furnace.
Label pieces of masking tape with the pen for each pair of wires. Affix each tape label to the wires.
Loosen, but do not remove the screws holding the wires. Each wire pulls off from below the screw head. The wires typically terminate in a Y-clip that fits under the screw head.
Adjust the multimeter to test for continuity. This is the "Ohms" setting.
Touch the two probes on the meter against each pair of screw terminals on the sequencer, one pair at a time. If the multimeter registers zero or the display numbers roll to infinity, that set of terminals is defective on the sequencer. Unfortunately, the entire sequencer must be replaced, even if only one set of terminals is broken.
Tips & Warnings
- Remove the mounting screws holding the sequencer inside the furnace and take the defective part to an HVAC parts supply store for a replacement. Leave the labels on the wires to reconnect them correctly to the new sequencer.