Blinking red light on furnace

The codes are usually explained on a wiring diagram that is on the back panel.

Check yours, it might be different!  For me, a continuously blinking light is normal.

  • Flashing slow: Normal – no call for heat
  • Flashing fast: Normal – call for heat
  • Continuous on: Replace IFC (circuit board)
  • Continuous off: Check power
  • 2 Flashes: External lockout (retries or recycles exceeded)
  • 3 Flashes: Pressure switch error
  • 4 Flashes: Open limit device
  • 5 Flashes: Flame sensed when no flame should be present
  • 6 Flashes: 115 VAC power reversed polarity or poor grounding
  • 7 Flashes: Gas valve circuit error
  • 8 Flashes: Low flame sense signal
  • 9 Flashes: Check igniter

FYI, for a modern furnace, Never attempt to light your furnace manually.  It likely uses a direct ignition system so when power is cycled, the pilot will then ignite automatically.  It’s better to just call your gas company if there was an outage.

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