Furnace locks out with E9, indicating a gas valve or fuel valve fault

Safety first: Turn off electrical power and close the gas shutoff valve. Gas work must comply with local codes; if you smell gas, evacuate and contact your gas supplier immediately.

Steps:

• Inspect wiring to gas valve: Locate the Danfoss gas valve on the burner train. Check the electrical connector for tightness and look for damaged wires.
• Check manual shutoff valves: Ensure all upstream manual gas cocks are fully open. Some valves have position indicators; verify they are aligned with the pipe.
• Listen for valve operation: With power restored and a call for heat, listen for a click from the gas valve when the control attempts ignition. No click may indicate a failed coil or no power from the control.
• Coil resistance check (if equipped and trained): With power off and wires disconnected, measure the resistance of the gas valve coil and compare with Danfoss specifications. An open circuit indicates a failed coil.
• Reset and test: After verifying wiring and valves, reset the controller. If E9 persists, the gas valve or control board should be replaced by a licensed gas technician.