Water heater does not start, display shows F0 immediately after power-up
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off the electrical supply to the water heater and close the gas valve before removing any covers. Wait for components to cool.
Steps to try:
- Power reset: Switch the unit off at the main switch or breaker for 2–3 minutes, then power it back on. Sometimes F0 is a temporary configuration read error.
- Check model configuration jumpers/dips: Remove the front cover and locate the main PCB. Verify that any configuration jumpers or DIP switches (e.g., for gas type or power rating) match the appliance label and Saunier Duval documentation.
- Inspect PCB for damage: Look for burn marks, swollen capacitors, or signs of moisture on the main control board.
- If F0 persists: The EEPROM or control board is likely corrupted. Do not attempt to reprogram the board without the official Saunier Duval service tool. Contact an authorized technician to replace or reprogram the main PCB.
Warning: Never bypass safety circuits or modify PCB wiring. Incorrect configuration can cause unsafe combustion or damage to the heater.
Repair Difficulty
Required Part
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