52
Rinnai Modulating Gas Valve or Combustion Control Fault

Boiler locks out with error 52; fan may run but ignition does not proceed correctly.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Faulty gas valve modulation coil, Incorrect gas valve wiring, Control PCB combustion control failure, Incorrect gas type or pressure

How to Fix / Troubleshooting

Safety first: Turn off power and gas. Do not attempt to adjust gas valves without proper training and calibrated instruments.

  • Visual inspection: Check the gas valve assembly for loose connectors, damaged wiring, or signs of overheating.
  • Confirm gas type: Ensure the boiler is configured for the correct gas type (natural gas or LPG) as per the rating plate and installation.
  • Check supply pressure (professional): A qualified technician should measure inlet and manifold gas pressures and adjust if necessary.
  • Component replacement: If wiring is intact and gas supply is correct, the gas valve or control PCB may need replacement by a Rinnai-trained technician.
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Repair Difficulty

Professional Required 5/5

Required Part

Modulating Gas Valve Assembly
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