Plastic helps coolant sensor survive hot engines

A low-coolant sensor from Entratech Systems, Sandusky, Ohio (www.entratechsystems.com), sits directly in radiators of trucks, off-road vehicles, and marine equipment. Conventional sensors generally consist of a metal probe tip immersed in the coolant. However, new hybrid organic-acid technology (HOAT) used in long-life engine coolants can corrode the probe through electrolysis. The Entratech sensor uses a stainless-steel probe. An onboard microchip processes proprietary ac signals that indicate coolant level. An indicator lamp alerts the operator when coolant drops too low. The circuit also features a time delay to prevent false alarms from coolant moving during operation.

The stainless-steel probe is insert-molded into a housing with integrated threads for mounting through a threaded hole in a radiator. The sensor housing is Amodel AS-1933 HS grade of polyphthalamide from Solvay Advanced Polymers L.L.C., Alpharetta, Ga. (www.solvayadvancedpolymers.com). The material resists temperatures to 275°F and won't degrade or change dimensions even after prolonged exposure to conventional glycol or HOAT coolants.