I have a Heil natural gas heater (p/n NUGK100DH03) The blower will not cycle off. The termistat is in the auto mode. I have a feeling it is either the main limit or the fan relay. Can some one let me know how I can tell??
Hi it can be a number of things but more than likely you are on right path with a limit switch either can be one of the rollouts with are normally located near the burners and have the red resets or it is the main limit which is above the burners is a little square with 2 screws holding it into the heat exchanger section easiest thing to do is first check manual resets on the rollouts then take a multimeter and check ohms or shut power off pull the wires off each side and check for continuity remember the switch is in the closed position it opens on safety also check your air filter !