Trane XR90 – What does the blinking red light mean?

Unfortunately, the user manual of the Trane XR90 furnace offers no explanation of  what the blinking light means that can be seen behind a small hole in the bottom front panel of this high-efficiency gas furnace.

The codes are explained on a wiring diagram that is glued to the back of the panel.

Trane XR90 Diagnostic Codes

Trane XR90 Diagnostic Codes


A continuously blinking light indicates normal operation and is no reason for concern. Here is the complete list:

  • 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

Dr. Heet does not provide support or repair advice for this type of furnace. Please contact a licensed HVAC professional if your furnace does not function properly.