Furnace shuts down with E15, indicating a flame detected when there should be no flame (false flame signal)

Safety first: Turn off power and close the fuel supply valve. Do not operate the furnace until the cause is identified.

Steps:

• Inspect flame sensor position: Remove the burner access and verify that the Danfoss flame rod is correctly positioned in the flame zone and not touching metal parts.
• Clean sensor: Gently clean the flame rod with fine abrasive pad to remove soot and oxidation. Avoid bending the rod.
• Check wiring: Trace the flame sensor lead back to the control. Look for points where the insulation may be rubbed through and contacting the chassis. Repair or replace damaged wiring.
• Reset and test: Restore power and fuel, then reset the control. If E15 reappears without any burner operation, the control's flame detection circuit may be defective and require replacement.