87F16 Furnace Primary Limit Switch up to 140°F

Key Features

• Primary high-limit safety control for forced-air furnaces
• Activates at a fixed temperature of 140°F (60°C) to prevent overheating
• Automatically resets at 110°F (43°C)
• Switch configuration: SPST (Single Pole, Single Throw), normally open contacts
• Probe insertion length: 3 inches

Replaces / Cross-Reference Part Numbers

• 87F16
• 87F1601
• L140-30F
• L140F-40
• 36T01B3

Compatibility & Fitment

• Designed as a direct replacement for specific Lennox brand furnaces.
• Verify fitment by confirming the part number on your original switch or in your equipment's service manual.

When to Replace

• Furnace blower runs continuously after the heating cycle has stopped.
• Heating system short-cycles or shuts down prematurely.
• Furnace fails to produce heat or ignite the burners.
• Control board displays a fault code indicating an open limit switch.

Installation Tips

• Disconnect all electrical power to the furnace before servicing.
• Locate the limit switch, typically mounted on the furnace plenum near the heat exchanger.
• Note wire connections before removing the old switch.
• Install the new switch, secure it with the mounting screws, and reconnect the wires to the terminals.
• Restore power and test the furnace through a complete heating cycle to ensure proper operation.