Daikin Wall-Mounted Indoor Unit FTXS18HVJU

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

1. Check to see 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 to see 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 tester.

Check the continuity between the pins 1 - 6 and 3 - 6, and between the pins 2 - 5 and 4 - 5. If there is no continuity between the pins, the EV coil is faulty.

4. If no EV generates 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 latching sound, and check to see if that EV generates latching sound.

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

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

Make sure that the voltage of 320 ± 30 V is applied.

1. Set operation off and power off. Disconnect the connector S70.

2. Check that the voltage between the pins 4 - 7 is 320 VDC.

3. Check that the control voltage between the pins 3 - 4 is 15 VDC.

4. Check that the rotation command voltage between the pins 2 - 4 is 0 ~ 15 VDC.

5. Keep operation off and power off. Connect the connector S70.

6. Check whether 2 pulses (0 ~ 15 VDC) are output at the pins 1 - 4 when the fan motor is rotated

Warning: This procedure should be performed by a trained technician

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

Upload a photo of the measured waveform

Is the power supply waveform a sine wave as shown in Fig.1?

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

Warning: This procedure requires trained personnel with PPE!

Install the inverter checker instead of a compressor

Charged voltage of the built-in smoothing electrolytic capacitor dropped to 10 VDC or below?

Terminals removed from the compressor?

Terminals connected to the terminals of the inverter checker without touching each other?

Activate the power transistor test operation from the outdoor unit

Forced operation [ON/OFF] switch pressed for 5 seconds?

Diagnose according to 6 LEDs lighting status

Warning: Disconnect the connectors of the thermistors from the PCB before proceeding

Thermistors disconnected from the PCB?

Measure the resistance of each thermistor using tester

The relationship between normal temperature and resistance is shown in the table and the graph below

The room temperature thermistor is directly mounted on the display PCB. Remove the display PCB from the control PCB to measure the resistance.

Display PCB removed from the control PCB?

Measure the resistance of the room temperature thermistor

When the indoor heat exchanger thermistor is soldered on the PCB, remove the thermistor and measure the resistance.

Indoor heat exchanger thermistor removed from the PCB?