Furnace displays E09, no heating, may occur after a power surge or wiring work.

Safety: Turn off power and close the gas shutoff valve before working inside the furnace.

Steps:

• Inspect gas valve connector: Locate the gas valve on the gas train and ensure its electrical connector is firmly attached and not corroded.
• Check wiring harness: Follow the wires from the gas valve back to the Cointra control board. Look for damaged insulation, loose plugs, or signs of overheating.
• Check fuses: Some control boards have onboard fuses protecting the gas valve circuit. With power off, visually inspect and replace any blown fuses with the exact same rating.

Professional service: Testing the gas valve coil resistance and verifying control board output should be done by a qualified technician. If the gas valve or control board is faulty, replacement must follow Cointra procedures and gas safety regulations.