You will need to replace the limit switch if it has stopped working. But if it is still working, it is protecting you against over temperature conditions and is part of a safety circuit. One the biggest causes for limit switches to open is the lack of air flow due to blocked coils, dirty filters or improperly operating fans. You should never operate a furnace with a safety circuit overridden.
You mentioned it started when jumpering a safety switch, if it is the flame rollout switch then most rollout switches have a reset button between the leads on the switch. Reset the switch is easy and should allow the furnace to restart. The rollout switch detects just that excess heat coming backward into the flame sword area. Some causes for this to occur is cracks in the heat exchanger, the induction fan deteriating so the flue gasses are not exhausted properly, or a blockage in the flue gas path. Blockage can be caused by excess rust buildup in the tubing, dirt dawber nests, and any number of other obstructions.
Any way you need a professional to determine the cause for the limit switch opening.
Hope this helps.
Sounds like you have and open limit switch trace the wires from the gas valve one will go straight to the terminal board the other one will go through all the safety limits take an ohm meter (an ohm meter beeps or lights up when you touch the leads together showing a direct connection also called continuity) and check each limit switch by touching one of the meters leads to one wire on the switch and the other meters lead to the other wire on the switch if no continuity is there your switch is open some switch's have little reset buttons on them. Find the open switch and reset or replace.
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