When a tankless unit won't fire up at all, the cause is typically no gas reaching the burner, a fault in the ignition or flame-sensing system, or restricted combustion air, and the unit's fault history usually narrows it down quickly.
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Quick answer
Ignition requires gas flow, a working igniter, and a flame sensor confirming the burner actually lit, all happening correctly in sequence, and a fault anywhere in that chain stops the whole process rather than causing a partial issue. In Coquitlam, wind-exposed terminations on hillside properties add restricted-airflow scenarios to the usual list of reasons a unit refuses to ignite.
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A gas shutoff valve that's accidentally closed, whether from recent work elsewhere in the home or simply being bumped, is the easiest thing to check before assuming a component has failed. If other gas appliances in the house are also not working, that points to a supply-side issue rather than something specific to the tankless unit.
An aging igniter or a flame sensor coated with residue over years of operation can cause the unit to attempt ignition, briefly establish a flame, and then shut the gas valve back down when the sensor fails to confirm that flame is present. This often looks like repeated, unsuccessful ignition attempts before the unit locks out entirely, rather than a single clean failure.
Homes higher up Burke Mountain or Westwood Plateau see more sustained wind at the vent termination, and strong wind pushing back into the intake can disrupt the combustion air supply enough to prevent stable ignition, even without any physical blockage. This tends to correlate with specific weather conditions, which is a useful detail to note when describing the problem.
A tankless unit needs electrical power for its control board and ignition system even though it's gas-fired, so a tripped breaker, a loose power connection, or a control board fault can all prevent ignition just as effectively as a gas supply problem. Checking whether the unit's display or indicator lights show any activity at all helps distinguish a power issue from a gas or ignition fault.
| Symptom pattern | Likely cause |
|---|---|
| Completely unresponsive, no lights or display | Power supply issue |
| Attempts ignition repeatedly, then locks out | Ignition control or flame sensor fault |
| Fails specifically during windy conditions | Combustion air disruption at the termination |
| Other gas appliances also not working | Gas supply issue upstream of the water heater |
Pulling the unit's fault code history is usually the fastest way for a licensed technician to confirm the exact cause rather than working through each possibility by trial and error.
Safety note
If you ever smell gas (a sulphur or rotten-egg odour) near your tankless unit, do not flip switches or search for the leak yourself. Leave the house, leave the door open behind you, and call FortisBC at 1-800-663-9911 from outside. Any work on the gas line, venting, or burner assembly has to be done by a Technical Safety BC licensed gas fitter.
Confirm the gas shutoff valve at the unit is fully open and check whether the unit has any power at all — a blank, unresponsive display points toward an electrical cause rather than a gas or ignition fault.
On wind-exposed hillside terminations, a strong gust pushing back into the intake can disrupt the combustion air supply enough to prevent the burner from establishing a stable flame, even without a physical blockage.
It's a sign of an ignition control or flame sensor fault that should be diagnosed by a licensed technician rather than reset repeatedly, since continued attempts without addressing the cause won't resolve it.
Yes, since the control board and ignition system both need electrical power, a tripped breaker or loose connection can prevent ignition just as completely as a gas supply problem.
You can safely check whether the shutoff valve near the unit is open yourself; anything beyond that, including diagnosing an ignition or flame-sensor fault, should go to a licensed gas fitter.
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