Furnace shows E20, often after a brownout or power surge.

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

Corrupted firmware, Damaged EEPROM, Overvoltage or surge damage, Manufacturing defect in PCB

Safety: Isolate power. Electronic repairs should be carried out by qualified personnel.

User action: Try a full power reset. If E20 persists, the PCB will likely need replacement.

Technician checks:

Verify supply quality and check for evidence of surge damage.
Attempt any manufacturer-approved reset or reprogramming procedure if available.
Replace the main PCB and perform all safety and combustion checks.

Hard 4/5

Main Control PCB

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