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