Furnace does not start, display shows E0 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 power to the furnace at the service switch and isolate the gas supply before removing any covers.
Steps:
- Remove the front service panel to access the main control board.
- Visually inspect the main PCB for burn marks, swollen capacitors, or damaged tracks.
- Check all low-voltage connectors (especially the multi-pin harness from the user interface to the PCB). Unplug and firmly reseat each connector.
- Verify correct mains supply at the input terminals with a multimeter (only if you are trained and competent). Incorrect voltage can prevent initialization.
- Restore power and see if the E0 code clears after a reboot.
- If E0 persists and wiring is sound, the control board firmware or hardware is likely defective and the board should be replaced by a qualified technician.
Do not attempt board-level repairs (soldering, component replacement) unless you are certified and the unit is out of warranty.
Repair Difficulty
Required Part
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