Hi,
I have a Trane XB80 (M/N TUE080A936L0) that is not lighting and blowing cold air. The blower and igniter comes on and it cycles through the lighting cycle, but the burners don't light. I don't have a service manual to properly troubleshoot but here is what I know so far...
-I just replaced the flame sensor with new OEM
-60 V AC is going to the flame sensor
-The LED flashes continuously, even after a couple of start cycles
-Using an ohm meter, the limit switch circuit is showing closed

To further complicate things, I just tried to check voltage to the gas valve (red and blue wires) and saw no voltage, but after reconnecting the wires nothing is happening with the furnace. I hear the electrical buzz but no blower, no LED, no nothing. I have flipped breakers, but still nothing. I can run down and get a control board for $115 but I just wanted to be sure it was not the gas valve (or anything else) first. Any help would be appreciated?
-tenntully

OK scratch the furnace not working at all part. The fuse fell out when I pulled the harness to the board. I just checking the gas valve wires for voltage as the furnace went through the lighting cycle and didn't see any voltage. I am not sure what it is supposed to see but it doesn't seem like the gas valve is getting a signal from the board. Does this sound like a bad board?
Thanks in advance for the help!!

Update: Got a new control board. Before I installed it, I wanted to check it one more time just to check the sequence again. Well this time the burners lit! It is running fine for the moment, but I fully expect this to be an intermittent issue. Any recommendations for shaking it out or should I just change the control board after it fails again?