market dynamics
Water - cooled spray motorcycle is not good to start, water temperature sensor may be the culprit!
Release date:2021.04.08

(1) What does the water temperature sensor do?

The water temperature sensor is basically the same as the temperature sensor in structure, but its function is to provide an analog signal of temperature change to the engine control unit.

Its power supply voltage is a 5V power supply provided by the control unit, and the signal returned to the control unit is a linear change signal of 1.3V ~ 3.8V. The main function is to tell the engine control unit what the current temperature is.

Its signal is extremely important to the control unit. The main reason is that the engine has different working methods at different operating temperatures. For example, below 86 degrees, the engine should be sprayed with 10% more oil than the normal temperature, in order to make the engine heat up quickly to reduce the low temperature wear of the engine. And when the temperature rises above 86 degrees, you want to make the engine spray a little less oil, you want to let the temperature rise a little more slowly.

If something goes wrong with the water temperature sensor and gives the wrong signal to the engine control unit, such as providing a cold signal to the engine while the car is being heated, the injector will spray more gasoline. Therefore, whether the water temperature sensor works normally or not is crucial to the normal operation of the engine.

The sensors for the water temperature gauge are supplied with a 12V power supply and the engine control unit is supplied with a 5V power supply, so they are not interchangeable. And the shape of the plug itself is different.

The difference is simple. The plug for the former has only one lead in it, while the plug for the engine control unit has two lead in it.


The function of the water temperature sensor is to convert the temperature of cooling water into electrical signals, which are input into the ECU:

1. Correct the amount of oil injection; Increase fuel injection at low temperatures.

2. Correct ignition advance Angle; At low temperature, the ignition advance Angle should be increased, and at high temperature, the ignition advance Angle should be delayed to prevent deflagration.

3, affect the idle control valve; At low temperature, ECU controls idle control valve action according to water temperature sensing signal to increase engine speed.

4, affect the EGR valve;

(2) What are the characteristics of the water temperature sensor?

Thermistor type water temperature meter is composed of thermistor type water temperature sensor and bimetallic strip water temperature meter. Among them, the thermistor is the sending part of the water temperature information, and the bimetallic electric heating wire is the receiving part, and the two are in series.

The sending part is the water temperature sensor installed in the channel and the cooling water contact, when the water temperature is low, the thermistor resistance value is higher, the current in the loop is small, the resistance wire calorie-value is small, the bimetallic sheet is slightly bent, indicating the needle in the low temperature area (C area).

When the water temperature is higher, the thermistor resistance value is small, the current through the loop is larger, the heat of the resistance wire is larger, the bimetallic sheet bending deformation is larger, the indicator needle points to the high temperature area (H area).

(3) How to judge that the water temperature sensor is out of order?

When the water temperature of the engine is low, the water temperature information input by the water temperature sensor of the water temperature meter into the ECU makes the air-fuel ratio denser, so as to make the engine work stably. If the water temperature sensor does not send out the cooler status information at this time, the air-fuel ratio will become thinner, leading to abnormal operation of the engine. Similarly, if the cooler information is sent after the warm machine, the air-fuel ratio will become thicker, and the engine will not work normally.

When the water temperature sensor fails, it often displays the temperature signal of the hot car when the cold car starts. The ECU can not provide the signal of too strong mixture, but can only supply the thinner mixture of the engine (the signal of the hot car). Of course, the cold car of the engine is not easy to start.