I have a Trane Gas Furnace, model # TUE120A96OK3, that is 6 years old. I am having an issue with it where the burners will not stay lit. I check the red LED light diagnosis, and it says that it is having an "open high limit device" error. I thought that I could possibly reset or replace this to fix the problem, but I do not know where the Limit Switch is. Do you know if you can reset this switch to fix this problem or does it need to be replaced, or where it is located? Thanks for your help.

Replace the limit and make sure you have good airflow. All registers open, filter is clean, blower motor and wheel are clean and the evaporator coil is clean.

My Trane American Standard gas furnace model is TUE100A948K2, manufactured 2000-2001. Had the same issue. The blower was on but no heat. Solution: The limit switches are connected with yellow wires. Found the defective switch near the blower's capacitor. The switch's contacts rusted out from the condensations dipping down from the AC cooling coil. (Be sure that the safety pressure switch is off before doing the next steps.) Took out the switch by removing two screws and cleaned the contacts. Reconnected the yellow wires and it worked. The local Trane parts center said they only sell parts to licensed contractors and warned me not to do the repairs myself. Called the contractor and could only get appointment two days later with estimated cost of $200. The switch's pixes are in my iPhone. The part should cost a few bucks online. I will upload the pixes when more time is available.

Update: There are actually two limit switches. The one I found on the big blower is called 2" limit switch. The other one is located on the left side of the small fan and is called 3" limit switch. My earlier post did not solve the problem as the blower stayed on forever and the flame did not ignite when I turned up the temperature. Found the 3" switch short and replaced it. Everything works. Easy to order the 3" switch online. Disclaimer: Don't attempt to do this if you don't have the necessary skills.