someone is adjusting the car ac

Figure 1: The car air conditioner.

Many car owners are puzzled to find their air conditioners starting frequently while driving. In fact, the normal start and stop period of the air conditioner is generally about 20-30 seconds. This article will take you to look at reasons and solutions for frequent startup of the Car air conditioner.

Energy Saving Mode

The energy saving mode is used. If so, the compressor will stop automatically after reaching the set temperature. When the temperature exceeds the set target temperature, the compressor will restart. Therefore, the air conditioner starts and stops frequently. In this case, you just can turn off the energy saving mode.

Insufficient or Excessive Refrigerant

Insufficient or excessive refrigerant causes frequent pressure changes in the compressor, resulting in the frequent startup of the air conditioner. At this time, you should go to a professional repair shop or 4S shop to check the refrigerant.

Blocked Car AC System

The air conditioner system is blocked. When the pipes are blocked, the pressure of the air conditioner system will be affected, resulting in a frequent start. At this point, you should clean the pipe to relieve extremely high or low pressures. For these types of faults, routine maintenance is also necessary.

For example, you should regularly check whether the pipes and components in the air conditioner system are loose or damaged, such as the compressor and expansion valve.

Inspect the belt tensioner and belt operation condition regularly.

Regularly clean or replace the filter of the air conditioner, and clean the air duct, so as to keep the air fresh into the car.

Examine whether the air outlet is blocked. If it is not cleaned for a long time, it may produce a peculiar smell.

Check the refrigerant regularly to ensure there is no leakage.

the structure of the car air conditioning compressor

Figure 2: The car ac compressor, composed of thrust bearings, valve shaft, swash plate, pistons, snap rings, oil, and O-rings and seal.

Compressor Protection Mechanism

Car ac compressor often starts and stops, which may be because of the compressor protection mechanism. There are three kinds, including thermal protection, extremely low temperature protection and overcurrent protection.

* Thermal Protection

If the system lacks Freon, the system will be blocked for a long time, the ambient temperature will be high, and the compressor thermal protection device will be damaged.

The specific reason for the frequent start and stop of the ac compressor depends on the actual situation. You should observe whether the fan of the air conditioner works normally. If the fan is running, it will indicate that the compressor is failed. It is also possible that the compressor is damaged or the overheat protection is working.

Ambient Temperature

If the weather is not hot, the working time of the compressor will be short. When the temperature in the car meets the setting requirements, the compressor will start and stop frequently.

There is a lack of suitable refrigerant in the ac system. It would lower the pressure. To protect the compressor, the pressure valve cuts off the power to the compressor, which can also cause the compressor to start frequently.

Extremely high and low pressure are both to protect the ac system. In short, as long as the air conditioner pressure is normal, the cooling degree of the ac can be achieved.


Car ac systems are divided into manual and automatic types. The manual air conditioner does not own AUTO mode, which is equal to the household air conditioner without frequency conversion function. Fixed-frequency air conditioners will continue to cooling after the temperature is set and turned on.

Old air conditioners need to stop when the temperature is low and then start again to adjust the temperature. Now the improved fixed-frequency air conditioner will stop as long as it reaches the preset temperature after setting the temperature and restarts the compressor and cooling after the temperature rises.

Suppose the temperature is set at 26℃, and after reaching it, the compressor stops, and then rises to 27℃, does it need to restart? The temperature fluctuation in summer will be very fast, so is the compressor going to start and stop at a high frequency? In fact, this is not the case. Fixed-frequency air conditioners can fluctuate within the "±3℃" of the set temperature, and there is a time buffer period.

The displacement compressor can not change the operation power, after starting, it will fully operate. The compressor will stop when the temperature reaches the set temperature and restart when the temperature rises. Cars, however, can heat up very quickly because of several efficient heat sources.

displacement compressor 5330429

Figure 3: The displacement compressor.

The internal combustion engine used in the petroleum vehicle will produce strong heat energy in operation, so the engine room can easily reach 70 or 80 ℃. Hot through the firewall heats the air inside the car efficiently, so it warms up quickly. Windows can basically filter ultraviolet light, but the core of heat generation is infrared. Windows only block part of the infrared, so you can control the temperature with shade.

Car body panels are mostly steel, with only a few using fiberglass-reinforced plastics . The thermal conductivity of the steel plate is very strong, even if there is a barrier of the interior plate, the heat will continue to conduct to the car, so the car will heat up quickly. If the vehicle in motion is using a manual air conditioner, the compressor will start and stop at a high frequency.

The compressor power of petroleum vehicles comes from an internal combustion engine. The displacement compressor loses the power of the engine at constant power all the time, and the engine has to increase the speed to compensate for the power, which will cause the problem of higher fuel consumption.

The variable displacement compressor can reduce the power after reaching the set temperature, which is to reduce the loss of engine power. Under the premise of sufficient power, it will not pull up the speed to compensate for the power, and the fuel consumption will naturally be lower. This is also the core factor of the recommendation to choose an automatic air conditioner system.


In any case, the frequent start and stop of the air conditioner compressor are abnormal. This is because, for the compressor of the refrigeration system, the frequent start and stop will lead to most of the refrigerating oil in the compressor into the system pipeline, which tends to cause the compressor to run without oil.

car automatic air conditioner

Figure 4: The automatic air conditioner system of the car.

The compressor plays the role in compressing and driving refrigerant in the refrigerant loop of the air conditioner.

Air conditioner compressors are generally installed in outdoor units. The refrigerant is extracted from the low-pressure part by the compressor and then compressed to the high-pressure area for cooling and condensation.

The heat is emitted into the air through the radiator, and the refrigerant also changes from gaseous to liquid form and the pressure increases.

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