Guide · 7 min read
Is It the Element or the Sequencer?
The single most common wrong order in electric heat. Ten minutes of testing tells you which part you actually need — and the two fail in very different ways.
What a sequencer does
A sequencer is a timing relay. Electric heat kits are built in stages, and if every stage energised at once the system would pull thirty to fifty amps in a single inrush — enough to trip breakers, dim lights and stress everything on the circuit.
So the sequencer staggers them. Each stage comes on a few seconds after the last, spreading the load over fifteen or twenty seconds. It is a small, cheap, entirely mechanical part, and when it fails it produces symptoms that look exactly like dead elements.
The rule that settles it
This one distinction resolves most cases:
Partial heat means elements. No heat at all means sequencer.
If some stages heat and others do not, the sequencer is demonstrably working on the stages that fire — so the dead stages are burned-open elements. If nothing heats at all, suspect the sequencer, the control board or the supply before you suspect every element failing simultaneously.
Elements do not usually fail together. They are independent components with independent failure points, so multiple stages going dead at the same moment points at something they share — which is the sequencer.
Testing it properly
- Isolate the circuit. Breaker off, verified dead with a non-contact tester at the unit. Electric heat circuits carry serious current.
- Open the heat kit compartment. You should see the elements as open coils, with the sequencer as a small block with several terminals nearby.
- Test each element for continuity. Meter on ohms, across each element's terminals. Note every reading — you are looking for which stages are open and which are intact.
- Interpret. All elements read correctly, no heat at all? Sequencer or control. Some elements open? Those are your failed parts.
- Check the sequencer coil. It should show continuity across its control terminals. An open coil means it cannot pull in at all.
Our resistance test tool will tell you whether each reading is healthy, degraded or open.
Other symptoms worth knowing
Breaker trips as soon as heat starts. Often a sequencer that has failed closed — every stage energising at once, exactly the inrush the sequencer exists to prevent.
Heat comes on, then quits after a few minutes. More likely a limit switch tripping on restricted airflow than either an element or a sequencer. Check the filter first.
Blower runs continuously, cold. Blower control works, heat call is not reaching the strips. Sequencer, board, or thermostat wiring.
Fix the airflow, or you will be back
If the elements failed because of restricted airflow — a blocked filter, a crushed return, a weak blower — new elements will fail the same way. Repeat element failure is almost always an airflow problem wearing an element's clothing.
Why this order goes wrong so often
Because the symptoms are genuinely identical from the thermostat. "I turned the heat on and cold air came out" describes both faults perfectly. Without opening the unit and testing, there is no way to tell them apart — and the parts are very different in cost.
If you are sending us an enquiry, tell us what each stage is doing rather than just "no heat". That one detail frequently identifies the fault before anyone touches a meter.
Common questions
Can I replace a sequencer myself?
It is a simpler swap than an element — usually a few spade connectors and two screws. But it sits in a high-current compartment, so the same rule applies: isolate the circuit, verify it is dead, and if you are not confident, get a technician. In Ontario much of this work is legally restricted anyway.
How long do sequencers last?
They are mechanical relays cycling thousands of times per season, so they are a genuine wear item. On a system old enough to have failed elements, a sequencer of the same age is worth testing while you have the panel open.
Should I replace both while I am in there?
If both test marginal, yes — you are already inside the unit and the labour is the expensive part. If the sequencer tests fine, leave it. We are not going to tell you to buy a part that is working.
Get a quote
Send us your model number or a photo
Most people who contact us do not know their part number, and that is fine. A photo of the rating plate or the old element is enough for us to identify the exact replacement.