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Cooling Water Tank Liquid Level Sensor Knowledge

Jul 17, 2023 | China News | 0 comments

Since the coolant level sensor of the diesel generator set is not directly installed on the tank to connect with the coolant, it reduces the failure rate of the water tank of the thermal heater, improves the sealing performance of the tank, and increases the service life of the sensor. At the same time, limit bosses are made on the upper and lower sides of the radiator water tank, the float will not fall off during the floating process, and the reliability is high. The magnetic ring of permanent magnetic material can ensure maintenance-free.

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Working principle of liquid level sensor

As the name implies, the water level sensor is a sensor used to detect the liquid level and realize the liquid level control function. When the water level in the radiator water tank is lower than the predetermined water level, the sensor gives a signal, and the water pump starts to add water automatically. Will not dry, will not spill, very convenient and practical.

  • The liquid level sensor (water level sensor) is a pressure sensor that measures the liquid level. The liquid level gauge is based on the principle that the static pressure of the measured liquid is proportional to the height of the liquid. It uses advanced isolated diffusion sensitive elements or ceramic capacitor pressure sensitive sensors to convert the static pressure into an electrical signal, and then undergoes temperature compensation and linearization. Correction, converted into a standard electrical signal (generally 4~20mA/1~5VDC).
  • The coolant level sensor is used to monitor the coolant level of the cooling system and transmit the information to the ECM through the diesel generator wiring harness. If the coolant level falls below a certain level, the CM will make the alarm alarm and the power of the diesel generator will decrease gradually to protect the diesel generator.
  • The voltage is detected on the No. 27 high liquid level signal terminal and J/ No. low liquid level signal terminal of the coolant level sensor of the diesel generator harness at the same time, or no voltage is detected on each terminal, and the ECM considers it to be Fault, and stored as fault code 422, then the yellow indicator light is on. Diesel generators will lose their coolant level protection.

Liquid level sensor installation location and functional characteristics

Installation location

The main function of the liquid level sensor is to detect the liquid level and control the liquid level. The coolant level sensor is a switch, which is installed on the radiator tank or in the radiator tank.


The coolant water level sensor used in the cooling system of the radiator water tank of the diesel generator includes an induction device sensor and an enabling device magnetic ring float. The sensing device sensor includes a maximum and minimum liquid level sensing circuit, a temperature sensing circuit and a heating circuit.

  • The maximum and minimum liquid level sensing circuit is used to judge the high and low movement status of the magnetic ring float of the actuator.
  • Temperature sensing circuit, used to detect the temperature of the coolant or the ambient temperature of the radiator tank.
  • Some models are equipped with a heating circuit to heat the coolant that freezes due to low ambient temperature.


In addition to being rugged and reliable, Dominus position sensors are suitable for long-term operation in harsh cooling lake applications. Compatible with cooling flow, Encore can be installed on any position egg of power generation equipment, making it an ideal OEM solution.

  • It has the ability to reduce the influence of medium conductivity to a low level in its operating frequency range, thereby ensuring long-term stable performance, and adopts a sealed design to prevent any fluid intrusion.
  • liquid level sensors are almost maintenance-free, small in size, anti-adhesion, and maintain reliability even in standby mode.
  • Operating temperature up to 125°C (257%F), making this capacitive sensor capable of handling challenging environments.
  • Various installation types and electrical connections are provided, and the installation is very simple.
  • Supply voltage range 9 to 32VDC.

Disassembly and detection of coolant water level sensor


  • Do not open the pressure cover of the radiator on the thermal oil generator, wait until the temperature of the coolant drops below 50C before opening the pressure cover, in order to avoid danger, drain enough coolant from the cooling system to drain the top of the radiator Radiator tank.
  • Lift the locking piece and pull the electrical connector apart, remove the coolant level sensor.


  • Install and tighten the new coolant level sensor, push the electrical plugs together until it locks, fill with coolant and check for leaks.


The resistance detection of the cooling water level sensor can be divided into two methods: the on-board detection method and the single-piece inspection method.

  • On-vehicle inspection method.

Put the ignition switch in the OF position, shake off the wire connector of the cooling water level sensor, and use a digital multimeter to test the electric value between the two terminals of THW and E2 of the sensor, and the resistance value is inversely related to the temperature.

  • One-piece inspection method.

Unplug the harness plug of the coolant temperature sensor, then remove the coolant temperature sensor from the diesel generator, place the coolant temperature sensor in the water in the beaker, heat the water in the cup, and measure the liquid temperature under different water temperature conditions with a multimeter at level 0. The resistance value between the two terminals of the bit sensor, and compare the measured value with the standard value. If it does not meet the standard, it should be replaced with a new sensor.

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