Why is My AC Compressor Not Turning on and What to Do?

Figure 1: Air conditioner outdoor unit.

The air conditioner compressor (AC compressor) is generally installed in the outdoor unit. When the air conditioner is running, the compressor sucks the refrigerant from the low-pressure area, compresses it, and then sends it to the high-pressure area for cooling and condensation. The heat is released into the air through the condenser, and the refrigerant also changes from a gaseous state into a liquid state, with increased pressure.

Then the refrigerant flows from the high-pressure area to the low-pressure area, and is sent into the evaporator through the capillary tube (or expansion valve). The pressure drops suddenly, and the liquid refrigerant immediately becomes gaseous, and absorbs a large amount of heat in the air through the condenser. This is the working process of an AC compressor.

Nowadays, air conditioners are very common household appliances. In the hot summer, problems such as AC unit not turning on, AC running but not cooling, AC wont turn off may occur. The most common problem is that the AC compressor does not start (AC compressor not turning on)? First of all, we must check the cause of the problem clearly, and then we can find the right way to solve it. Usually the air conditioner compressor does not start for the following reasons.

1. Why is My AC Compressor Not Working and How to Fix?

The compressor is a very important component in the air conditioner. So what are the reasons for the AC compressor not turning on? 9 reasons why the air conditioner compressor does not start are as follows:

●Poor Power Connection
●Compressor Capacitor and Relay Damaged
●Dirty Outdoor Unit
●Lack of Refrigerant
●Unstable Condensing Pressure
●Low Voltage
●Nonstandard Installation
●Compressor Wear
●Lock Function

After finding out the relevant reasons, you can solve the problem that the air conditioner compressor does not start by yourself or ask someone professional to solve it according to the relevant solutions.

1.1 Poor Power Connection

The power cord of the air conditioner is not plugged in properly, the power cord is not in good contact, or the power cord is aging, which will cause the air conditioner compressor to fail to work.

Solution: It is recommended to check regularly whether the air conditioner wires and household sockets are damaged.

1.2 Compressor Capacitor and Relay Damaged

It is also very common that the air conditioner compressor cannot work properly due to damage to the compressor capacitor and relay.

Solution: Check whether the relevant accessories in the circuit are damaged.

Figure 2: Broken capacitor.

1.3 Dirty Outdoor Unit

If the outdoor unit is too dirty, the heat dissipation of the air conditioner will not be good, and the load on the compressor will be increased, after a long time which may damage the compressor and cause the compressor to not work.

Solution: clean the outdoor unit.

1.4 Lack of Refrigerant

If the air conditioner has insufficient refrigerant and works in this state for a long time, the air conditioner compressor will also fail.

Solution: First check whether there is a leak point in the air conditioner, and then add refrigerant to the air conditioner.

Figure 3: Adding refrigerant for air conditioner.

1.5 Unstable Condensing Pressure

If the condensing pressure is too high, the high pressure relay will be activated to stop the operation of the compressor; if the suction pressure of the compressor is too low, the low pressure relay will also be activated to stop the operation of the compressor.

Solution: Check the cause of unstable condensing pressure and eliminate it, and restore the condensing pressure to the normal pressure range.

1.6 Low Voltage

If the voltage used by the air conditioner is too low, lower than 10% of the single-phase normal voltage, it is difficult for the refrigeration compressor in the air conditioner to start.

Solution: If the local power supply voltage is often in a low state, please choose a reliable power supply voltage stabilizer to use. At the same time, families with more electrical appliances can use a dedicated power supply.

1.7 Nonstandard Installation

When the air conditioner is installed, if the air inside the air conditioner system is not drained cleanly, it will lead to ice blockage, which will increase the load of the compressor when the air conditioner is in operation, causing the temperature of the compressor to increase. The refrigeration oil will deteriorate at high temperature for a long time, which cannot perform the function of lubricating and cooling effects, further increasing the temperature of the compressor. The insulation of the coil is reduced due to high temperature, causing the compressor to be damaged and not to work.

Solution: In the process of installing the air conditioner, strictly follow the standard operating specifications.

1.8 Compressor Wear

The internal wear of the compressor is serious, which makes it unable to work normally. The compressor plays a vital role in the air conditioning system, and its main job is to compress and deliver the refrigerant.

Solution: Replace the air conditioner compressor.

Figure 4: Inverter AC compressor.

1.9 Lock Function

Some brands or models of air conditioners have a lock protection function. If the lock mode is started, no operations can be performed. Besides, if the compressor works at high temperature for a long time, the coil insulation will decrease, the resistance value will be too low, the starting current will increase, and the temperature of the compressor will rise instantly, which will also activate the air conditioner lock protection.

Solution: Unlock the air conditioner according to the manual or ask a professional for help.

2. What to Do When My AC Compressor Does Not Start?

1. First of all, you can check the power supply voltage of the air conditioner to see if there is a power failure. For example, if there is a short circuit in the line, the air conditioner compressor will not work. Check whether the power supply voltage of the air conditioner is sufficient. If the power supply voltage is relatively low, the compressor will not work.

If there is a problem with the power supply voltage during the maintenance of the air conditioner, it is necessary to take corresponding measures.

2. If there is no problem with the power supply voltage, then it is necessary to check whether the main board of the air conditioner’s outdoor unit is abnormal. The main board of the outdoor unit is mainly to control the operation of the outdoor unit components and receive the communication signal from the indoor unit. If the main board fails, the AC compressor will not work.

During the maintenance of the air conditioner, it is necessary to check the main board.

Figure 5: Checking the main board of the outdoor unit.

3. If there is no problem with the above, then it is necessary to check whether the start capacitor of the AC compressor is normal. If the compressor start capacitor is damaged, it will naturally cause the compressor to fail to work.

If the start capacitor is broken, it is necessary to replace it.

4. In addition, if the AC compressor does not work, there may be a problem with the compressor itself. For example, if the refrigeration oil is too little or deteriorated, it will cause the compressor to jam, so that the compressor cannot be started.

During the maintenance of the air conditioner, if the compressor itself has quality problems and cannot be repaired, the compressor needs to be replaced.

5. Failures in other aspects will also make the compressor not work, such as compressor overheating protection, compressor high and low pressure protection, etc. During air conditioning maintenance, it is necessary to conduct a comprehensive inspection for the reasons why the compressor does not work.

3. How to Tell If My AC Compressor is Bad?

The following phenomena appear during the use of the air conditioner, indicating that there may be problems with the air conditioner compressor:

1. When the air conditioner is turned on, it can operate normally, but the cooling effect is poor.
2. If the air conditioner is running, it is found that the noise and vibration are obviously larger than usual.
3. After the air conditioner is running for a while, it is found that the surface of the compressor is hot, and then the compressor cannot be started again.

Figure 6: Air conditioner outdoor unit on the ground.

4. How to Prevent AC Compressor Not Turning on?

4.1 Avoid Frequently Turning on and off the Air Conditioner

Some consumers like to turn on and off the air conditioner frequently, thinking that it can save electricity, but actually it is not. The engineer suggested that the air conditioner should be controlled by itself (auto mode) so that the compressor can work more efficiently.

4.2 Turned on the Air Conditioner Once a Month

Even in the season when the air conditioner is not used, it is necessary to develop the habit of turning it on at least once a month. Because if the air conditioner is not used for a long time, the refrigeration oil in the compressor may condense, and the compressor may be stuck when the air conditioner is used again after a long time.

4.3 Clean the Condenser Regularly

When the air conditioner is in use, the dust in the air will block the gaps in the condenser, resulting in poor heat dissipation and the pressure of the condenser increasing, which will increase the current of the compressor motor and make the air conditioner consume more energy. After the compressor operates at high power consumption for a long time, its working life will be reduced.

Therefore, engineers suggest that consumers should clean the condenser regularly. Generally, when the air conditioner is frequently used in summer, it is best to clean and disinfect the radiator once a month.

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