Service manual

- 4 -
Fan/Limit Control
The Fan/Limit Control shuts the furnace down in an Over-Temp situation. This usually
involves the room air fan. The fan may be defective or the fan may need cleaning. If the
squirrel cage becomes dirty, they can’t move enough air to keep the furnace cool enough
when running on the higher settings. If the High Limit trips more than once a closer look
should be given to Convection Blower of the furnace. The Fan/Limit Control may
actually be causing the problem if it is not controlling the fan correctly. The control is
adjustable and the settings should be looked at when troubleshooting this area. Setting the
Limit setting too low could cause the unit to shut down at the incorrect temperature.
NOTE: The Room Air Fan (Convection Blower) is wired independently from the
Control Board. Keep in mind when troubleshooting this area of the furnace that
replacing the Control Board will not fix any issues related to the Blower and
Fan/Limit Control.
NOTE: A dirty Filter may cause the furnace to run hotter and may contribute to the
unit shutting down. Check the filter and replace if needed.