how to test water temp sensor gauge

• 2022-07-14

How to test the vehicle water temp sensor gauge ? First , check the power supply voltage: Unplug the plug and use the two probes of the multimeter to check whether the voltage between the two lines is about 5V as the reference voltage (some models directly provide 12V voltage to the water temperature sensor, such as the water temperature gauge). Then , Read the data flow: the normal water temperature signal is generally about 95 ℃ (high temperature engine is about 115 ℃). If the water temperature sensor signal is abnormal, repair it. For example, if the water temperature signal shows -40 ℃, it means that the negative pole is open or short circuited, and if there is no change at 130 ℃, it means that the positive pole is short circuited (some cars will show it at 140 ℃). Third , Resistance detection: heat the water temperature sensor, and then measure its resistance (when the external temperature is 30 degrees, the resistance is about 1.4 K ω To 1.9 K ω).

After the engine cooling water temperature sensor fails, the engine is difficult to start in cold air, the idle speed is unstable, and the power is insufficient when accelerating. In the hot engine state, the power is normal when the engine starts, idles and accelerates. The engine fault indicator is always on. When the engine cannot find the normal signal of the coolant temperature sensor, in order to keep the engine running, the engine will perform the safety function. Use the cooling water temperature substitute value stored in the memory as the cooling water temperature value. When the engine is in cold air, the control injection quantity lacks the increase related to the low engine temperature, the mixture becomes lean, and the engine is difficult to start.

The temperature sensor is made of semiconductor material, so the voltage is 5V. When the plug is unplugged, the voltage is 5V. Plug in the plug and it will be more than oneortwo volts. Different vehicles have different values. The sensor has a negative temperature coefficient. According to Ohm's law, u=ir, the higher the temperature, the lower the resistance and the lower the voltage. As long as the signal voltage changes from high to low, it is generally normal. You can also measure the sensor resistance. The water temperature is about 90 and the resistance is 8900 ohms. And we only need to convert the intake air volume into different telecommunications to control it. The intake air volume is also a basic signal that determines the fuel injection volume.