I'm fighting a problem on our house gas furnace. Every once in awhile, the furnace will run but no heat. Indicator on the control board indicates a problem in the "high limit" circuit. Those two sensors are good, confirmed with trusty meter. Reseated the connections at each sensor, still had the problem. Unplugged/plugged the 12-pin connector at the control board, then it works fine. Next step will be to meter the limit switch loop from that connector, and check the control board connector pins for cold solder joints.
1987 Avion 34W
1995 Ford F250 7.3L PowerStroke