Carrier 42QFD048D8S Service Manual page 90

Remarks:
• Use a multimeter to test the DC voltage between 2 port(or S or L2 port) and 3 port(or N or S port) of outdoor unit.
The red pin of multimeter connects with 2 port(or S or L2 port) while the black pin is for 3 port(or N or S port) .
• When AC is normal running, the voltage is moving alternately as positive values and negative values
• If the outdoor unit has malfunction, the voltage has always been the positive value.
• While if the indoor unit has malfunction, the voltage has always been a certain value.
• Use a multimeter to test the resistance of the reactor which does not connect with capacitor.
• The normal value should be around zero ohm. Otherwise, the reactor must have malfunction.
Note: The picture and the value are only for reference, actual condition and specific value may vary.
 Troubleshooting
S and N
L2 and S
2 and 3
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or
or