Rinnai Tankless Water Heater Error Code 05: How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
Summarize with ChatGPTSummarize with ClaudeSummarize with Perplexity Add as Preferred Source on Google
Error Code
05
Brand
Rinnai
Product Type
water_heater
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Error code 05 on your Rinnai tankless water heater indicates a bypass servo position fault. The bypass servo controls water flow through the heat exchanger; when it malfunctions, the heater may not regulate temperature properly. This guide will help you troubleshoot and fix the issue.
Ad

Tools You'll Need

How to Fix Error Code 05

  1. Power Cycle the Water Heater

    Always turn off the power supply before opening any panels.

  2. Check the Incoming Water Supply

  3. Inspect the Bypass Servo Wiring

    Disconnect power before handling internal components.

  4. Clean the Servo and Surrounding Area

    Be gentle to avoid damaging the servo mechanism.

  5. Test the Servo with a Multimeter

    Only perform if comfortable using a multimeter.

  6. Replace the Bypass Servo

    Ensure the replacement part matches your model number.

Parts You May Need

Rinnai bypass servo
Check Price on Amazon
Rinnai bypass servo
Check Price on Amazon
Rinnai bypass servo
Check Price on Amazon
Rinnai bypass servo
Check Price on Amazon
Ad

When to Call a Professional

If you've completed all steps and error persists, or you're uncomfortable testing electrical components, contact a qualified Rinnai technician. The control board may need replacement, which requires professional diagnosis.

Frequently Asked Questions

Can I bypass error code 05 temporarily?
No, bypassing the error is not recommended. The bypass servo is critical for safe operation. Running the heater with this fault could cause overheating or damage.
Will error code 05 clear itself?
Sometimes a power cycle clears the code if it was a temporary glitch. However, if the fault is persistent, it will return unless the root cause is fixed.
How much does it cost to replace a Rinnai bypass servo?
The part typically costs between $50 and $150. Professional installation may add $100-$200 labor.
What causes error code 05 on Rinnai water heaters?
Common causes include a stuck or failed bypass servo, loose wiring, low water pressure, or a defective control board.
Can I use my water heater with error 05?
It's not recommended. The heater may not heat water properly and could be unsafe. Best to troubleshoot and fix the issue.

Related Error Codes