Abstract: An apparatus for cooperation with an existing opening within a cooling radiator of a vehicle for determining the liquid level in the radiator. The radiator, which may be an automobile or truck radiator, is connected to an electrical power source of the vehicle through the vehicle chassis. An insulator is established relative to the vehicle radiator in a substantially fixed relation. A sensor is mounted to the insulator for extending into the liquid in the radiator when a sufficient quantity of liquid is contained therein. The sensor has a plurality of curved surfaces for increasing the surface area of the sensor. An indicator interconnects the sensor with the electrical power source of the vehicle for indicating the level of liquid contained in the radiator by conductivity through the liquid in contact with the sensor. The increased surface area of the sensor enables the indicator means to be a conventional incandescent lamp connected in series with the sensor and the electrical power source of the vehicle.