Furnace displays Er12 and will not start; may occur after a power surge or outage.

Safety first: Disconnect power before touching the control board or wiring.

Steps:

• 1. Hard reset: Unplug the furnace for at least 10 minutes. During this time, press and hold any keypad button for 10 seconds to help discharge residual power. Plug back in and check if Er12 clears.
• 2. Inspect power supply: Verify that the furnace is connected to a properly grounded outlet with stable voltage. Consider using a surge protector to prevent future damage.
• 3. Check board connections: Remove the control panel cover and gently press on all connectors to ensure they are fully seated. Look for burnt components or damaged traces on the board.
• 4. Factory reset (if available): Some US Stove control boards allow a factory reset via a button sequence. Refer to your model’s manual and perform the reset if supported.
• 5. Replace the control board: If Er12 persists and the furnace will not operate, the control board is likely defective. Replace it with the correct US Stove control board, or have a qualified technician perform the replacement and configuration.