We have a tempstar model 867769426 it has a fan limit switch on it when the furnace calls for heat the exaust fan turns on the burners start and the limit switch starts turning as it is turning it all the sudden it jumps about a 1/8 of a turn and shuts the burner off the blower motor won't start if I pull the limit switch back by hand it will start the blower. What should the switch be set at and would it be possible to pull the switch out and oil it so it moves freely and doesn't jump when trying to work maybe clean it up when removed also