Trane SWT1280 Limit Switch or an audible humming sound

or an audible humming sound from the outdoor unit without ignition

maintaining smooth operation in standard indoor mechanical environments

Use a multimeter to check for continuity across the load terminals after the control circuit is energized

10 WC pressure switch ensures that the inducer motor is moving sufficient air to safely vent combustion gases before the ignition sequence initiates

Trane SWT1280 Limit Switch or an audible humming soundThe Trane SWT1280 Limit Switch is a high reliability OEM thermal protection component specifically engineered for HVAC furnace safety and consistent air handler performance. This 3" insert limit switch serves as a critical fail safe, monitoring supply plenum temperatures to prevent equipment damage. It is factory calibrated with a 155F opening point and an automatic reset that closes the circuit at 125F. For field technicians, the SWT1280 is identical