Daikin PE-ADDA200 Service And Installation Manual page 51

While testing the diode in reverse bias, thus reversing the test leads as shown in above example for the W-
phse of the inverter (still with the diode test mode selected on the multimeter) the multimeter should
indicate OL (open switch).

A good forward-based diode displays a voltage drop >0.1 volts, typical 0.3~0.4V The multimeter
displays OL when a good diode is reverse-biased. The OL reading indicates the diode is functioning
as an open switch. When doing the voltage drop test , and the mesured value is 0.1V or lower the
diode, and thus complete IGBT module should be considered faulty!.

A bad (opened) diode does not allow current to flow in either direction. A multimeter will display
OL in both directions when the diode is opened.
Daikin Applied Europe S.p.A
SERVICE and INSTALLATION MANUAL
Compressor Inverter PE-ADDA200
Fig. 34
Fig. 35
Page 51 of 51
Rev. 0.3