Why a Slant/Fin boiler fails to ignite, the difference between pilot and electronic ignition systems, and how a licensed technician tracks down the cause.
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Quick answer
Ignition failure on a Slant/Fin boiler generally comes down to one of a few causes: a weak or fouled igniter, insufficient or unstable gas supply pressure, a dirty burner, a failed flame sensor, or a control board fault. Diagnosing which one applies requires measuring gas pressure and testing ignition components directly, which is licensed gas fitter work, not a homeowner task.
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Older Slant/Fin boilers commonly use a standing pilot with a thermocouple, where a small continuous flame lights the main burner when the thermostat calls for heat. Newer models typically use electronic ignition, either a hot surface igniter or a spark igniter, that lights the burner directly without a continuous pilot flame. The two systems fail in different ways, which is why knowing which type your boiler has matters for diagnosis.
A standing pilot that keeps going out often points to a weak thermocouple or a draft issue in the mechanical room, while an electronic ignition system that fails to light more often points to a worn igniter, a flame sensor that isn't detecting the flame correctly, or a gas valve issue.
| Ignition Type | Common Cause | What a Technician Checks |
|---|---|---|
| Standing pilot | Weak or misaligned thermocouple, draft blowing out the pilot | Thermocouple output, pilot flame position, draft sources |
| Hot surface igniter | Cracked or degraded igniter, low voltage supply | Igniter resistance, board voltage output |
| Spark ignition | Fouled electrode, poor grounding, gap out of spec | Electrode condition, gap, grounding continuity |
| Any system | Insufficient gas supply pressure | Manometer reading at the gas valve |
You can watch and listen for a click or spark attempt followed by no flame, note whether there's a gas smell during the attempt, and check that the gas valve to the boiler is fully open. You should not attempt to relight a standing pilot repeatedly if it keeps going out, and you should never hold down a gas valve or bypass a safety switch to force ignition.
If you smell gas during a failed ignition attempt, or notice the smell lingering afterward, treat it as a gas safety situation and leave the home before calling FortisBC.
Ignition failures are one of the more common service calls on any boiler brand, and most are resolved with a cleaned or replaced igniter, a corrected gas pressure issue, or a burner cleaning rather than requiring a full boiler replacement.
Boilers installed in damp, unheated basements common in older Vancouver-special homes are more prone to condensation forming on electrical connections and igniter components over a wet coastal winter, which can contribute to intermittent ignition faults that seem to come and go with the weather. A technician checking for ignition failure in these homes will often pay particular attention to the condition of wiring connectors and the general dryness of the mechanical space, not just the igniter itself.
Homes on hillside or exposed lots can also see draft-related pilot or flame disturbances during heavy wind, which is worth mentioning if your ignition problems seem to line up with particular weather conditions rather than happening at random.
Safety note
If you smell gas near a Slant/Fin boiler, hear hissing at a gas fitting, or a carbon monoxide alarm activates, leave the home right away and call FortisBC at 1-800-663-9911 from outside before doing anything else. Combustion, venting, and gas piping work on a boiler must be done by a Technical Safety BC licensed gas fitter.
A click without ignition usually means the igniter or electrode is attempting to spark but the gas isn't lighting, which can point to a gas supply issue, a fouled electrode, or a control board timing fault.
You can try once following the instructions on the boiler's label, but if it goes out again shortly after, stop and call a licensed gas fitter rather than repeating the process, since a recurring pilot outage usually has an underlying cause.
Many ignition failures are resolved with a component like an igniter, thermocouple, or electrode, which is a modest repair compared with full boiler replacement, though the exact scope depends on what's found.
Yes, insufficient or unstable gas pressure at the valve can prevent reliable ignition even when the igniter itself is working correctly, which is why pressure is checked directly with a manometer.
This pattern usually points to a weak flame sensor signal rather than an ignition problem itself; the boiler lights, but the control can't confirm the flame is stable, so it shuts the gas valve as a safety measure.
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