trane xl 80 trouble shooting. the red warning light is flashing 4 times. it is an open high limit switch. what is this and can i fix it.
Check to be sure that you have enough registers open. Approx. 75% min. Check to be sure your filters care clean. Check gas pressure is to the factory setting 3.5" WC for gas. Pull Center limit, let cool and then check continuity. These are the most common problems. There are others but try this first.
PROBLEM:Trane XL80, Model # TDE060A936M1 gave error code of "Open Temperature Limit circuit" represented by 4 flashes on the control board LED. Technician diagnosed the problem to be a failed control board and quoted me $575 to replace it.
SOLUTION:The female pin head for the wire from the Temperature Limit Switch housed inside the plastic casing was pulled and did not connect to the male pin on the control board. When I pushed the wire to push the female pin head further inside the plastic housing, it made contact with the male pin on the control board and my gas burner started after a shutdown and restart. Finally, I got heat but it took a lot of troubleshooting to find the simple problem.
TROUBLESHOOTING DONE:+ Replaced the control board with brand new control board # CNT 03797. Bought it from eBay for $95.+ Cleaned the temperature gauge rod. This is a thin rod (on left side of the burners) that is bent to be in the line of the flames. It gives the signal to shut off the igniter (on right side of the burners).+ Jumped the Temperature Limit Switch using a paper clip connecting the 2 wires.+ Looked for any limit switches that were tripped.
ABOUT THE TEMPERATURE LIMIT SWITCH: It is the size of a credit card and is stuck on the inside wall right above the gas burners with 2 wires connected to it. It is essentially a meta disc that will expand if the temperature rises too much. It is the only limit switch on the Trane XL80 that does not have a manual reset button and so you most likely have to replace it if it is tripped but sometimes taps on the face of the limit switch can help restart the furnace short-term.
Several people have shared their experiences online, which helped me a lot to troubleshoot. I hope my experience helps somebody too. Good luck ? Mihir Rao
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