My 8 year old Trane Model tuh2d120a9v5va furnace is not giving out heat. The service people are all busy due to the recent storms. Through the little glass viewing window I see red and green flashing lights. The red flashes 4 times, the green 3 times, and these overlap. The panel inside says the 4 flashing red means an open limit switch.
Where do I go from here?
Update: A 1" flat capacitor in the fan control module was fried black and cracked. A new module and $1000 later and the heat works again. Perhaps the power fluctuations due to the storm here caused some spikes that fried the module. I might put a surge protector on the line to the HVAC.
Best Answer
The high temp limit switches usually have a manual reset button that needs to be pressed to reset. I would try a reset it may have been a fluke that it tripped, if the reset dosent trip again it is probably fine. If it trips again you will want to verify the exhaust is clear, and the fan is freely spinning (some do need oil at each end to lube the bearings) low air flow on a high efficiency system can overheat the fire box.