Daikin Indoor Unit Ceiling Mounted Cassette Type Heat Pump FFQ18Q2VJU

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

Thermistors disconnected from the PCB

Measure the resistance of the room temperature thermistor

Note: The data is for reference purpose only

Room temperature thermistor removed from the control PCB

Measure the resistance of the indoor heat exchanger thermistor

Indoor heat exchanger thermistor removed from the PCB

Sign off on the thermistor resistance check

Check No.16: Make sure that the voltage is within 320 VDC.

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

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

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

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

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

6. 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).

Check the connection of connector

Check motor power supply voltage output (pins 5 ~ 8)

Check motor control voltage (pins 5 ~ 4)

Check rotation command voltage output (pins 5 ~ 3)

Check rotation pulse input (pins 5 - 2)

Sign off on the connector output check

Check No.22: Make sure that the voltage between (+) and (–) of the power module is approximately 0 V before checking.

Voltage between (+) and (–) of the power module is approximately 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?

Follow the procedure below to measure resistance between the terminals of the power module and the terminals of the compressor with a multimeter.

Enter the resistance measurement between the terminals of the power module and the terminals of the compressor

Evaluate the measurement results

Sign off on the power module check

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

Check if the power supply waveform is a sine wave (Fig.1)

Check if there is waveform disturbance near the zero-cross (sections circled in Fig.2)

Sign off on the power supply waveforms check