Gas and Oil Home Heating Furnaces - open high limit device won't reset???

I have a Trane XE80 gas furnace and it won't run. It keeps showing an open high limit device and when I cycle the power off and on to reset the controller the unit will try to start normally and trip off on the open high limit device.
The thing has'nt run all day so it's not hot. I put a new filter in and the fan is running correctly. I have all the books and I'm looking at the print and schematic now.Any suggestions?

If you have an OHM meter, I'd take one wire off, and then see if the switch is open or closed.

If it's open on you if the furnace has not been running all day. Then you need to replace it.

I don't know about this particular furnace but often high limit switches have a manual reset. If you lknow where the limit switch is physically located I suggest that you look for a button or lever to use in resetting.

If you don't have an ohm meter. Use a jumper wire instead. By putting a jumper wire across the terminals you will be able to identify the culprit.

A word of caution however, turn off the power when doing all this. You don't want to hurt yourself and if you knick a wire you'll blow the transformer which will cost you more and then you still have the orginal problem.

Ok, I checked the circut, there are 4 switches in series. I ran down the line and checked for continuity across the entire line from HL1 to HL0. There are 2 flame roll out switches and 2 high temp limit switches. The circut is complete. I plugged the connector back into the terminals on the board and the damn thing runs fine. There's 24 VAC across the circut and I've no idea what I did. I've half a mind to replace all the switches in the circut and the controller. Any ideas?

May of had a bad connection or dirty.

Hope it works from now on.