After the vehicle is started, there will be a warm-up process. When the engine is warming up, the water temperature rises slowly. The length of this time depends on the water temperature detected by the water temperature sensor. If the water temperature sensor is normal, it may be that the water temperature rises slowly due to the circulation of the thermostat. It is recommended that car owners mainly check the following two aspects: whether the thermostat is normal (can be judged by the temperature difference between the radiator inlet pipe and outlet pipe when getting in the car), and whether there is any abnormality in the electric fan. The reasons why the car's water temperature cannot go up are mostly due to these three common reasons: 1. The thermostat is turned on too early or normally; 2. The electric fan rotates frequently; 3. The water temperature sensor is damaged. Damage to the water temperature sensor will cause a "false fault problem", that is, the actual water temperature is normal but the sensor falsely reports the water temperature. In addition, instrument misalignment may also lead to false hypothermia. The reason why the car water temperature rises slowly may be related to the outdoor temperature. Check whether the thermostat, water temperature meter, sensor, circuit, instrument, etc. indicate accurately, and whether the cooling fan control operation is abnormal. At the same time, if the time to turn on the heater is delayed, the air volume is too large or the external circulation method will affect the car heating. The reason for the low engine water temperature may be that the thermostat is damaged, causing the thermostat to be unable to close the valve, or the cooling fan keeps running due to malfunction. The thermostat is a control valve that controls the circulation of coolant in the cooling system, including large circulation and small circulation. If the thermostat is left open, the coolant will continue to circulate, causing the water temperature to drop.