My trane xr90 furnace keeps resetting just while it is in its "heat up phase" I'm a laymen but a description of what is happening is like this... The furnace gets a call for heat, it makes a sound and lights up near the burners, when the burners start to heat up it makes a "whisk" sound an restarts the process. This continually happens soon after the burners begin to heat up and before the fan begins to blow the warm air into the ducts. The filter is new, the red light is blinking fast and steady (when it is calling for heat). Sometimes if I switch off the breaker and reset it will work once or twice and then start failing again. Any ideas?


Check the flame sensor. Sounds like the furnace may not be sensing that the burners are on. Also, consult the manufacturers documentation for trouble code light sequences. The flashing light might be trying to tell you something.

Unconfirmed Trane Error Codes

Codes are displayed using a light (LED) turning on a number of times, followed by a pause. For example:

. = On _ = Off

Would be read as 4 flashes, and would mean that one of the limit switches was open.

  • Flashing Slow - Normal - No call for heat
  • Flashing Fast - Normal - Call for heat
  • 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 - 120V power supply polarity reversed, or poor grounding.
  • 7 Flashes - Gas valve circuit error.
  • 8 Flashes - Low flame sense signal.
  • 9 Flashes - Check igniter.

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