Buderus Pre-Ignition Sequence Stalled

Water heater fan runs but burner does not ignite and no error code is shown.

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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

Air pressure switch not proving, Blocked flue or intake, Weak fan not reaching required speed, Faulty gas valve not opening

How to Fix / Troubleshooting

Safety: Turn off power and gas. Combustion and venting work must follow local codes.

  • Check air pressure switch: Inspect tubing to the air pressure switch for kinks or blockages. Ensure connections are tight.
  • Test switch: With a multimeter, verify that the pressure switch closes when the fan runs. Replace if it does not operate correctly.
  • Inspect venting: Check intake and exhaust for obstructions and correct installation.
  • Gas valve check: A technician should verify that the gas valve receives an open signal and opens during ignition sequence.
  • Re-test: After clearing obstructions and replacing faulty parts, restore power and gas and observe the ignition sequence.
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Repair Difficulty

Professional Required 5/5

Required Part

Air Pressure Switch / Combustion Fan / Gas Valve
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