Daikin Outdoor Unit Cold Climate Multi-Split Type Air Conditioner 4MXL36WVJU9

Before this check, be sure to check the main circuit for short circuit.

With the circuit breaker still on, measure the voltage according to the drawing of the model in question. Be careful never to touch any live parts.

To prevent an electrical shock, use a multimeter to check that the voltage between FU2 and DC– is 50 V or less.

The surface of the test points (DC–) may be covered with the coating. Be sure to make firm contact between the multimeter probes and the test points.

Before this check, be sure to check the main circuit for short circuit.

With the circuit breaker still on, measure the voltage according to the drawing of the model in question. Be careful never to touch any live parts.

To prevent an electrical shock, use a multimeter to check that the voltage between DC + and DC – is 50 V or less.

Conduct the followings to check the electronic expansion valve (EV).

1. Check if the EV connector is correctly inserted in the PCB. Match the EV unit number and the connector number.

2. Turn the power off and on again, and check if all the EVs generate latching sound.

3. If any of the EVs does not generate latching sound in the above step 2, disconnect that connector and check the continuity using a multimeter.

Check the continuity between the pins 5 - 1, 5 - 2, 5 - 3, 5 - 4. If there is no continuity between the pins, the EV coil is faulty.

4. If no EV generates a latching sound in the above step 2, the outdoor unit PCB is faulty.

5. If the continuity is confirmed in the above step 3, mount a good coil (which generated latching sound) in the EV unit that did not generate a latching sound, and check if that EV generates a latching sound.

If a latching sound is generated, the outdoor unit PCB is faulty.

If a latching sound is not generated, the EV unit is faulty.

Warning: Ensure the voltage between (+) and (–) of the power module is about 0 V before proceeding

Voltage between (+) and (–) of the power module is about 0 V

Disconnect the compressor harness connector from the outdoor unit PCB. To disengage the connector, press the protrusion on the connector.

Compressor harness connector disconnected from the outdoor unit PCB

Measure resistance between the (+) or (–) terminal of the power module and the U, V, or W terminal of the compressor with a multimeter.

Enter the resistance measurement

Evaluate the measurement results

Sign off on the power module check

Warning: This check requires trained personnel with PPE!

Measure the power supply waveform between No. 1 and No. 2 on the terminal strip

Upload a photo of the measured waveform

Is the power supply waveform a sine wave (Refer to Fig.1)?

Is there waveform disturbance near the zero-cross (sections circled in Fig.2)?

Sign off on the power supply waveform check

Check to make sure that the voltage between (+) and (–) of the diode bridge (DB1) is about 0 V before checking

Measure the resistance between the pins of the DB1 referring to the table below.

If the resistance is infinity or less than 1 k, short circuit occurs on the main circuit.

2. Remove the top plate (10 screws).

3. Remove the right side plate (6 screws).

4. Remove the front plate (1 screw).

The front plate is heavy, so take care.