Combustion fan replacement on a tankless unit is a moderate repair, and diagnosis, part availability, and venting condition are what actually shape the cost.
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Quick answer
A tankless water heater's combustion fan is generally replaced once a licensed technician confirms worn bearings, a failed motor winding, or a fan wheel that will not reach proper speed even after cleaning, rather than a blocked vent or a faulty pressure switch, which can produce similar symptoms without the fan itself being at fault. What affects the cost for a specific home is correctly isolating the fan as the true cause, part availability for that unit's make and model, and access to the unit's combustion chamber. A licensed technician provides a firm number after diagnosis.
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A fan replacement is a smaller, contained repair and does not fall under the ballpark for a full tankless installation, roughly $3,500 to $7,500, which covers a whole new unit rather than a single component. Your technician gives a firm figure once the fan is confirmed as the cause.
Metro Vancouver's wet fall and winter months mean falling leaves, wind-blown debris, and occasional light snow at outdoor vent terminations are common contributors to airflow faults that can look identical to a failing fan from the homeowner's perspective. Before assuming the fan itself needs replacing, it is worth having the vent termination checked, since clearing a blocked vent is a much smaller job than a fan assembly replacement.
Safety note
Combustion fan replacement involves a sealed gas combustion system and must be performed by a licensed gas fitter. If you ever smell gas near the boiler or water heater, leave the home immediately and call FortisBC at 1-800-663-9911 before doing anything else.
A technician tests fan speed and motor condition directly and inspects the venting separately; the two can produce very similar symptoms, which is why proper diagnosis matters before ordering a part.
Yes, for the duration of the repair, though on a straightforward job with the part on hand this is typically completed in a single visit.
It varies by brand and model; some technicians carry common fan assemblies for popular tankless brands, while less common models may need to be ordered.
Not always; if the noise is from debris on the wheel rather than worn bearings or a failing motor, cleaning may resolve it without a parts replacement.
Warranty terms are set by the manufacturer and vary by model and installation date, so check your specific certificate before assuming coverage either way.
Keeping the outdoor vent termination clear of leaves and debris, and having the unit checked during annual maintenance, are the most practical ways to catch fan and airflow issues early.
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