Where Is the Furnace Limit Switch Located?
Published: July 23, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC
Location
The limit switch is typically located on or near the heat exchanger plenum (the large metal box above or behind the burners). It looks like a small metal disc or rectangle with two wires connected to it. There may be a small reset button in the center of some limit switches.
Visual Identification
The limit switch has two wire terminals and is mounted to the plenum with one or two screws. It may have a manual reset button (red or black) on the face. Some high-efficiency furnaces have multiple limit switches — one for the heat exchanger and one for the supply plenum. All are located in similar positions.
Testing the Limit Switch
With the furnace off, disconnect the wires and set your multimeter to continuity. Touch the probes to both terminals. At room temperature, the switch should be CLOSED (continuity). If the furnace has recently overheated and the switch tripped, it may be OPEN — press the manual reset button if present.