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Rinnai · Tankless water heater

65 Water flow control device (servo) fault

Medium severity Non-SENSEIRH180 hybridSENSEI RX/CXSENSEI

What the control is telling you

The water flow control servo is faulty; the servo valve did not close during the bath fill function.

Applies to: SENSEI Series, SENSEI RX/CX Series, Non-SENSEI Series

Likely causes

  • Loose, broken or damaged servo wiring
  • Water flow control servo failed to close
  • Failed water flow control servo
  • Incorrect servo resistance or supply voltage at the PC board

Test and repair steps

  1. Inspect the harness from the water flow servo valve to the PC board for loose, broken or damaged connections.
  2. Cycle power off and on and see whether the code clears.
  3. Because the servo failed to close during bath fill, shut off the water flow right away and stop using the bath fill controller.
  4. Warning: Turn off the electrical, gas and water supply to the heater before continuing.
  5. Replace the water flow control servo.
  6. SENSEI At connector D: red #18–pink #20 = 44–52 Ω; white #16–blue #14 = 44–52 Ω; grey #30 (black near the board)–orange #12 = 12–14 VDC.
  7. SENSEI RX/CX At CN9: red #16–pink #17 and white #15–blue #14 = 40-60 Ω; grey #5–orange #9 = 11-13 VDC; grey #5–brown #13 = under 1 VDC with limiter on, 4-6 VDC with limiter off.

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Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.55. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.