A liquid level assembly for controlling liquid level has a switching mechanism responsive to the liquid head to activate a pump. A housing assembly has an internal cavity in which the switching mechanism is supported, the housing assembly having an open end sealed by a diaphragm seal having a flexible planar portion that transmits head pressure to the switching mechanism. The diaphragm seal also has a peripheral web portion and a flexible bellows portion connecting the flexible planar portion and the peripheral web portion. The peripheral web portion has a peripheral sealing bead that is sealingly compressed against a groove in the housing assembly, and a plurality of knob members extend from the peripheral web to press against the switching assembly, thereby accommodating manufacturing dimensional tolerances of the switching mechanism.

A system and method for indicating required maintenance of an air filter used with an internal combustion engine. The system includes a throttle plate for adjusting an amount of airflow passing into cylinders of the engine. The system includes a throttle plate position sensor and a processor. The processor is responsive to a throttle plate position signal produced by the throttle plate sensor, for determining, as a function of such throttle plate position signal, whether the air filter is in need of maintenance. When a manifold absolute pressure sensor is provided, the processor is responsive to a first reading of such manifold absolute pressure sensor taken at a first time and at a second reading of the manifold absolute pressure sensor taken at a second time, for determining, as a function of a difference between such first and second readings whether the air filter is in need of maintenance.