Controller shows E6, burner stops and will not restart until reset, often after a power disturbance

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

Steps:

• Power-cycle the system: Turn off the furnace at the breaker for at least 2–3 minutes, then restore power. This can clear transient internal errors.
• Inspect control connections: Remove the control compartment cover and gently check that all multi-pin connectors on the Danfoss controller are fully seated. Look for bent pins or signs of overheating.
• Check grounding: Ensure the furnace chassis and control board ground connections are tight and free of corrosion. Poor grounding can cause logic errors.
• Verify supply voltage: If you have a multimeter and training, confirm that the supply voltage to the controller is within the range specified on the data plate. Significant over- or under-voltage requires an electrician.
• Configuration reset (if supported): Some Danfoss controls allow a factory reset via keypad or jumper. Follow the specific furnace manual instructions. Do not change combustion or safety parameters without proper documentation.

If E6 persists after these steps, the control board is likely defective and should be replaced by a qualified technician using the correct Danfoss replacement module.