Rinnai Tankless Water Heater Error Code 34: How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
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Error Code
34
Brand
Rinnai
Product Type
water_heater
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Error code 34 on a Rinnai tankless water heater indicates an air-fuel ratio control fault. This means the unit's combustion system is not operating within normal parameters, often due to blocked vents, gas supply issues, or a faulty fan motor. Before attempting repairs, ensure the unit is powered off and the gas supply is closed.
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Tools You'll Need

How to Fix Error Code 34

  1. Turn Off Power and Gas

    Never work on a water heater while it is connected to power or gas. Ensure the area is well-ventilated.

  2. Inspect Air Intake and Exhaust Vents

  3. Check Gas Supply Pressure

    Gas pressure testing should only be performed if you have the proper tools and experience. Otherwise, call a professional.

  4. Inspect the Fan and Fan Motor

    Ensure the unit is disconnected from power before opening the cover. Components inside may be hot.

  5. Reset the Water Heater

    If the error persists, do not repeatedly reset the unit as this may cause damage. Proceed to call a professional.

Parts You May Need

Fan motor assembly
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Fan motor assembly
Check Price on Amazon
Fan motor assembly
Check Price on Amazon
Fan motor assembly
Check Price on Amazon
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When to Call a Professional

If the error code persists after checking vents, gas pressure, and the fan motor, or if you are uncomfortable working with gas or electrical components, contact a licensed gas technician or Rinnai service professional.

Frequently Asked Questions

Can I still use my water heater with error code 34?
No, error code 34 indicates a combustion fault. Operating the unit may lead to unsafe conditions or further damage. Turn off the unit and troubleshoot.
How do I reset my Rinnai water heater after error code 34?
Turn off the power and gas for 5 minutes, then restart the unit. Press the reset button if present. If the error returns, a component is faulty.
What causes error code 34 on a Rinnai tankless water heater?
Common causes include blocked air intake or exhaust vents, low gas pressure, a faulty fan motor, or a malfunctioning air-fuel ratio sensor.
Do I need a professional to fix error code 34?
Basic checks like cleaning vents and resetting can be done DIY. However, if the error persists, call a professional due to the gas and combustion components involved.
How much does it cost to fix Rinnai error code 34?
If DIY, costs are minimal. If a technician is needed, expect $150-$300 for diagnosis and labor, plus parts if replacement is required.

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