Look for visible cracking

as using an incorrect replacement regulator spring can lead to pressure hunting or lock-up issues

Engineered as a normally closed safety device

Efficient Troubleshooting: A standard cold resistance of 40-100 ohms simplifies the diagnostic process for identifying failed ignition modules

Lennox 42J03 Limit Switch Look for visible crackingThe Lennox 42J03 Limit Switch is a critical safety component designed for precise thermal regulation within residential and commercial HVAC systems. This genuine OEM replacement part, also identified as part number 42J0301, features a fixed temperature range of 150 190F with an automatic reset function. As a veteran grade furnace high limit switch, it monitors the plenum temperature and breaks the electrical circuit to the gas valve if overheating is