Furnace shows E19, indicating a modulation or gas valve positioning fault on a modulating Danfoss burner

Safety first: Turn off power and gas. Modulating gas valve adjustments must be performed by qualified personnel.

Steps:

• Visual inspection: Locate the modulating gas valve and actuator. Check for obvious mechanical damage or disconnected linkages.
• Check actuator wiring: Inspect the control cable from the Danfoss controller to the actuator for damage or loose connectors.
• Listen for movement: During a call for heat (with panels in place), you may hear the actuator move. No movement or erratic noise suggests actuator failure.
• Do not adjust settings: Do not attempt to recalibrate or mechanically adjust the gas valve without combustion test equipment and the Danfoss service manual.

If E19 persists, the modulating gas valve assembly or actuator should be replaced and commissioned by a licensed technician.