E09
De Dietrich Gas Valve Control or Modulation Fault

Display shows gas valve / modulation error, burner may light but not modulate 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 modulating gas valve on De Dietrich burner, Loose gas valve connector, Faulty control board gas output, Incorrect gas type or pressure

How to Fix / Troubleshooting

Safety first: Gas components must only be adjusted or replaced by licensed personnel. Do not attempt to open the gas valve.

User-level checks:

  • Reset the unit: Power cycle the heater and reset any lockout.
  • Check gas supply: Ensure the main gas cock is fully open and that other gas appliances function normally.
  • Visual inspection: With power off, remove the front cover and confirm the gas valve wiring harness is firmly connected and undamaged.

When to call a professional: If E09 persists, a technician must test gas pressures, verify correct gas type configuration, and possibly replace the gas valve or control board.

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Repair Difficulty

Professional Required 5/5

Required Part

Modulating Gas Valve
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