Abstract: The present disclosure relates to a coolant level sensor device for application in vehicles, comprising three interoperable component parts: a housing component, an interchangeable cartridge assembly, and a resistor pigtail. The housing component may be configured to permanently and/or semi-permanently reside within the engine cooling system such that the housing component may receive the interchangeable cartridge assembly selectively connected with the resistor pigtail. The interchangeable cartridge assembly may comprise a reed switch that may be replaceable when damaged. Further, the interchangeable cartridge mechanism may be configured to connect with the resistor pigtail, which may include at least one resistor, such that the at least one resistor may be removed from close proximity to the high temperatures generated by the engine, thus increasing the life of the resistor components.