won,t stay running

i have a xe 90 trane furnace that lights but then shuts down after 10-15 sec

[joe]

Hey Eric, typically, when a unit runs and shuts down so quickly, the flame sensor is not working properly. This usually allows the unit to run about 5 seconds, however, and then shuts down. It will retry several times before "giving up" and going into "lock out" mode.

Whenever your furnace has a problem, it will go into lock out mode. When this happens, the LED light on the control board blinks a series of flashes to direct you to the problem. Look for this light through the site glass in the door when the problem occurs and count the flashes. You will have a sticker chart in the furnace that interpets the fault codes for you. Good luck!

NorthAmericaHVAC.com
Joe