Illustration of a technician using a multimeter to test a circuit board inside a tankless water heater.

Rinnai Code 61 (Combustion Fan Failure)

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Rinnai code 61 means the control board isn’t seeing the combustion fan spin up or reach the expected speed. The fan drives fresh air in and exhaust out, so this is treated as a combustion-safety fault, not a nuisance code.

Illustration of a technician using a multimeter to test a circuit board inside a tankless water heater.
Illustration of a technician using a multimeter to test a circuit board inside a tankless water heater.

Likely Causes, Ranked

  1. Failed fan motor
    Bearings wear out or windings fail after years of service.
  2. Fan speed sensor fault
    The board can’t confirm the fan is actually turning even if the motor runs.
  3. Wiring or connector issue between board and fan
    Vibration over time can loosen a connector.

Step-by-Step Diagnosis

  1. PRO ONLY
    Don’t attempt to bypass or force-run the unit

    This code exists because the unit can’t confirm safe combustion airflow.
  2. PRO ONLY
    A technician will typically check fan continuity, voltage at the connector, and the fan’s physical spin freedom before replacing anything.

FAQ

Is Rinnai code 61 a DIY fix?

No. It’s an electrical/mechanical fault in the combustion safety system — this is technician territory.

Written by HotWater Decoded — water heater repair specialists. Technically reviewed by a licensed technician on our team.

Sources

  • General diagnosis pattern for combustion-fan fault codes on gas tankless units

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