This Donaldson filter blockage sensor monitors the pressure differential across the engine air filter. It signals when the filter element is loaded to the point that airflow restriction could reduce engine power or increase fuel consumption. The sensor threads into the filter housing or the intake piping downstream of the element; a rising pressure drop across the filter triggers the sensor’s internal switch, which illuminates a cab warning lamp. A failed or clogged sensor gives a false warning or no warning at all, leaving the operator unaware of a restricted intake. The sensor is manufactured to the same thread and sealing geometry as the original component, so it seats correctly in the housing without adapters or sealant. On installation, apply thread sealant to the NPT threads and tighten to the housing manufacturer’s torque specification.