My furnace kicks the burner off when the fan starts. After 30 seconds the burner comes back on and then it runs through its cycle pretty much like it's supposed to. I was told by a Trane technician that it could either be the control panel orthe high limit switch. Where is the high limit switch located on a Trane XR80?

Look on the inside of the blower access door for a wiring diagram. Then follow it to the high limit.