I have a Trane XR80 furnace, with a self-check flash code system (flashing red light). The furnace has been blowing cold air when turned on, and not heating up. The red light flashes 4 times, indicating that we have an "open Temperature Limit circuit". I believe that this means that our temperature limit switch is not working correctly, or there is some other reason that the limit switch(es) are open, rather than closed. My thoughts are that the switch must be closed in order for the operation to proceed to whatever it takes to heat up the air. I would personally like to change the Temperature limit switch, which looks like a very easy task (according to the photo of the temp limit switch). Am I correct in my evaluation of the problem, and does anyone know How to change the switch?
Thank you