This is a picture of a flame rollout safety switch it will trip at a set temperature. The temperature set point of the rollout is designed to open when the flame is coming out the front of the burners
Possible heat exchanger has a hole or big crack.
Another possible cause is a combustion air intake pipe getting a plugged screen, Which will cause the room to work in A negative air pressure. Then air will be pulled in through the exhaust vent pushing flames out of heat exchanger and tripping the switch.
Between the wires the switch has a resettable button, but the cause of the problem should be found before leaving furnace. Never jump safety switch as it could cause property damage.
Thank you for visiting my blog I would appreciate any feedback I can get, Please leave a comment on whether my information has helped you. I am always interested in more topic to write so feel free to leave a comment asking about anything related to HVAC-R (Heating, Ventilation, air conditioning, refrigeration).
Thanks for reading my blog