Which sensors are used in the automobile air conditioning system?

The sensors of automatic air conditioning system mainly include outside temperature sensor, inside temperature sensor, evaporator temperature sensor, sunshine sensor, coolant temperature sensor, air quality sensor, smoke sensor and engine electronic control unit input signal. (Common faults include: sensor wiring short circuit or open circuit, sensor fault, etc. )

The following is the function and working principle of each sensor:

First, the automobile temperature sensor

Also known as indoor temperature sensor, it is one of the important sensors of automatic air conditioning. Usually installed in the suction device behind the dashboard, it will affect the air temperature at the outlet, the speed of the blower, the position of the air inlet and the position of the mode door.

Function:

1. Determine the position of the mixing door, thus determining the temperature of the air outlet.

2, determine the speed of the blower, so as to determine the air volume of the air outlet.

3. Determine the position of the intake valve, thus affecting the temperature and freshness of the air inside the car.

4. Determine the position of the mode door.

According to the different ways of forcing air to flow to the in-vehicle temperature sensor, the in-vehicle temperature sensor can be divided into two types: electric type and getter type.

Second, the external temperature sensor.

Also known as ambient temperature sensor, outside air temperature sensor or atmospheric temperature sensor. Generally installed in front of the front bumper or radiator, it can affect the temperature of the air outlet, the speed of the blower, the position of the intake mode door and the working state of the compressor.

Function:

1. Determine the position of the mixing door, thus determining the temperature of the air outlet.

2, determine the speed of the blower, so as to determine the air volume of the air outlet.

3. Determine the position of the intake valve, thus affecting the temperature and freshness of the air inside the car.

4. Determine the position of the mode door.

5. Control the compressor.

Third, the evaporator temperature sensor

Working principle: By detecting the evaporator surface temperature, correct the position of the mixing door, control the compressor, and stop the compressor when the evaporator surface temperature is lower than a certain value to prevent the evaporator surface from frosting.

Some models have two evaporator temperature sensors, one for correcting the position of the mixing door and the other for preventing the evaporator from frosting.

Thermistors of evaporators are generally installed on the heat transfer sheet of evaporators, and some are installed at the outlet of evaporators to measure the temperature of air coming out of evaporators.

Fourthly, the coolant temperature sensor

Adopt negative temperature coefficient, generally installed in heating device. Detect the temperature of the coolant and send corresponding signals to the air conditioning controller to control the preheating control.

There are two ways to obtain the coolant temperature in automobile air conditioning: one is to use a separate coolant temperature sensor, and the other is to obtain the coolant temperature signal through the engine ECU.

Function:

1. Measure the temperature of the heat exchanger core and correct the position of the mixing door.

2. It has a protection function to prevent the compressor from working when the engine is at high temperature.

3. Control the blower, and start the preheating control of the blower when the coolant temperature is low.

Five, sunshine sensor

Generally, it is installed on the dashboard that is easy to detect the change of sunshine, close to the bottom of the windshield. The photodiode in the solar sensor can detect the change of solar radiation and convert it into a current signal to be transmitted to the air conditioner controller.

Working principle: By detecting the intensity of sunlight on the sensor, the optical signal is converted into a voltage or current signal, which is transmitted to the air conditioning controller to correct the position of the mixing door and the speed of the fan.

Six, air quality sensor

Also known as multi-function sensor, it is mainly used to measure the moisture in the air, the ambient temperature and the pollution degree of the outside air. The air conditioning control unit controls the operation of the compressor and the position of the intake valve through its measurement results.

The measuring element of air quality sensor is mixed oxygen sensor, and its accuracy is improved by increasing the amount of catalytic additives platinum and rhodium.

Seven, smoke concentration sensor

Installed in the rear air conditioning unit.

Working principle: When the ignition switch is turned on and the air conditioner is in automatic mode, the smoke concentration sensor will start to detect the smoke concentration and send a signal to the air conditioner controller to control the rotation speed of the rear blower motor.