Rinnai Tankless Water Heater Error Code 66: How to Fix It

Q: What does error code 66 mean on a Rinnai water heater?

Error code 66 indicates a jammed or stuck servo motor in the water control valve, preventing proper water flow modulation.

Q: Can I still use hot water with error code 66?

No, the water heater will typically shut down or fail to ignite when this error appears. Hot water will not be available until the issue is resolved.

Q: How much does it cost to replace a servo motor on a Rinnai water heater?

The servo motor part costs around $50–$150, and labor for a professional can add $100–$200. DIY repairs save the labor cost.

Q: Will error code 66 clear itself?

No, the error will persist until the servo motor is freed or replaced. Restarting the unit may temporarily clear it, but the error will return if the motor is still jammed.

Q: What causes a servo motor to jam?

Common causes include mineral scale buildup from hard water, debris in the valve, or internal motor wear over time.

Abstract

Error code 66 on your Rinnai tankless water heater means the servo motor that controls water flow is jammed or stuck. This typically prevents the unit from firing up or maintaining temperature. You can often resolve this by checking for blockages or debris, but it may require a replacement if the motor is damaged.