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When the voltage between any two phases in the three-phase power supply of the outdoor unit of the air conditioner is only a dozen volts, and the voltage between any one phase and the zero line is 220 volts, the reasons why the air conditioner cannot be started may be as follows:

Power supply problem:

There may be faults in the power supply line, such as phase failure, poor contact or line aging, resulting in abnormally low voltage between the two phases.

There may be a problem with the power transformer or power system, resulting in unstable or unbalanced output voltage.

Unbalanced three-phase power supply:

During normal operation, the three-phase power supply should be balanced, that is, the three-phase voltage and current should be roughly equal. If the three phases are unbalanced, the voltage of some phases will be abnormal.

Motor failure:

The motor of the outdoor unit of the air conditioner may fail, resulting in short circuit or open circuit inside the motor, thus affecting the voltage distribution of the three-phase power supply.

Control line problem:

There may be faults in the control circuit of the air conditioner, such as the damage of relays, contactors, fuses and other components, which leads to the failure to transmit power to the motor normally.

The following measures can be taken for troubleshooting and maintenance.

Check the power cord:

Carefully check the power supply circuit of the outdoor unit of the air conditioner to see if there are problems such as phase failure, poor contact or circuit aging.

If a line fault is found, it should be replaced or repaired in time.

Check the three-phase power supply:

Use professional voltage measuring tools to check whether the three-phase power supply voltage is balanced.

If three-phase imbalance is found, check the power transformer or power supply system and take corresponding repair measures.

Check the motor:

Check the motor of the outdoor unit of the air conditioner for faults, such as internal short circuit or open circuit.

If the motor fails, it should be replaced or repaired.

Check the control circuit:

Check the control circuit of the air conditioner to see if there are any relays, contactors, fuses and other components damaged.

If the control circuit is found to be faulty, the corresponding components should be replaced or repaired in time.