Daikin Indoor Unit Floor Standing Type Air Conditioner FDMQ24WVJU9

Warning: This procedure requires trained personnel with PPE!

Disconnect the connector of thermistor ASSY from the PCB to measure the resistance between the pins using multimeter.

Enter the measured resistance value of the thermistor

Does the measured resistance value match the listed value?

To check the thermistor soldered on a PCB, disconnect the PCB from other PCB/parts, and measure the resistance between the both ends of soldered thermistor.

Enter the measured resistance value of the soldered thermistor

Does the measured resistance value of the soldered thermistor match the listed value?

Note: When replacing the defective thermistor(s), replace the thermistor as ASSY.

Sign off on the thermistor resistance check

Ensure that the voltage is within 320 VDC

Set operation off and power off. Disconnect the connector S70 or S71

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

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

Check that the rotation command voltage between the pins 4 - 2 is 0 ~ 6.5 VDC

Keep operation off and power off. Connect the connector S70 or S71

Check whether 4 rotation pulses (0 ~ 15 VDC) are input at the pins 4 - 1 when the fan motor is rotated 1 turn by hand

When the fuse is melted, check the outdoor fan motor for proper function

If NG in step 2 -> Defective PCB -> Replace the outdoor unit PCB (main PCB)

Voltage between (+) and (–) of the diode bridge (DB1)

If voltage is not about 0V, stop the procedure and report the issue

Resistance between the pins of the DB1

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

Does the main circuit have a short circuit?

Sign off on the main circuit short check

Warning: This check requires trained personnel with PPE!

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

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

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

Upload a photo of the measured waveform

Sign off on the power supply waveform check

Warning: This procedure requires trained personnel with PPE!

Install an inverter analyzer 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 analyzer?

Activate the power transistor test operation from the outdoor unit.

Power transistor test operation activated?

Diagnose method (Diagnose according to 6 LEDs lighting status.)