Lennox 12L38 L185-40F Furnace High Limit Switch

Description

Lennox 12L38 L185-40F Furnace High Limit Switch

The Lennox 12L38 is an OEM replacement high limit switch designed to protect your furnace from dangerous overheating conditions. Carrying the model designation L185-40F, this limit switch opens at 185°F and automatically resets once the heat exchanger temperature drops back down by 40°F (closing at approximately 145°F), providing reliable, automatic overheat protection for residential and light-commercial furnace applications.

How It Works

The high limit switch continuously monitors heat exchanger temperature. If airflow is restricted — due to a dirty filter, blocked vents, or a failed blower — temperatures can rise to unsafe levels. When the sensed temperature reaches the 185°F trip point, the limit switch opens the circuit, shutting down the burner to prevent heat exchanger damage or fire. Once temperatures fall to the reset threshold, the switch automatically closes and normal operation resumes.

Key Features

• OEM Lennox replacement part — ensures proper fit and function
• Opens (trips) at 185°F to protect against furnace overheating
• 40°F differential — automatically resets at approximately 145°F
• Designed for use in Lennox furnace applications
• Provides automatic, self-resetting overheat protection
• Helps prevent heat exchanger damage and potential fire hazards

Specifications

• Brand: Lennox
• Part Number / SKU: 12L38
• Model: L185-40F
• Trip Temperature: 185°F (opens on temperature rise)
• Differential: 40°F
• Reset Temperature: Approximately 145°F (automatic reset)
• Component Type: High Limit Switch

Application

This limit switch is a direct OEM replacement for compatible Lennox furnace models. Always verify compatibility with your specific furnace model number before ordering. Proper installation by a qualified HVAC technician is recommended.