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The genuine OEM Lennox 16V72 is a contactor equipped with an integrated auxiliary switch. Beyond its main function of switching high-voltage power to the compressor and condenser fan when cooling is called for, the built-in auxiliary contact provides a secondary signal used by the control board to confirm contactor status or to interlock additional components in your Lennox system.
Common signs of a failing unit include a buzzing or humming coil, main contacts that stick closed and run the compressor continuously, pitted or burnt terminals, and an outdoor unit that won't energize. When the auxiliary switch itself fails, you may see control-board faults, improper staging, or accessories that no longer respond even though the compressor operates.
OEM matters especially for this part because the auxiliary switch configuration, contact ratings, and coil are engineered specifically for your Lennox equipment's control logic. A standard contactor without the auxiliary contact will not provide the required feedback signal. Installing the factory 16V72 ensures full compatibility, correct control operation, and dependable rated performance.