Hitachi RAC-25YH4, Service Manual, Page: 114 / 121

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By connecting CN3 and CN4.
Check the voltage between "+15V" and
"15-0V" on power P.W.B.
By disconnecting CN3 and CN4.
Check the voltage between "+15V"
and "15-0V" on power P.W.B.
Diagnosis procedure of IPM using multimeter.
<Inverter section>
Set the multimeter function to resistance x 100.If the multimeter dose not have x 100 range, please select
its range from x 1 to x 100.
The judgment shall be OK. When the measurement was high resistance.
(Please consider that the probe polarity will be reserve when use a digital mulimeter due to its battery
connection inside)
<note>
Sometimes, it may misjudge as OK because of low conductivity when power module was damaged as
disconnect mode. In this case, please check the resistance by reversing the probe polarity and consider
OK when it was low resistance. Also, it is OK if the resistance was as same as the other phases (U,V,W).
<Driver circuit (internal IC)>
15V will not be generated when the internal IC has malfunctioned.
To find the malfunction either the power supply of power P.W.B or internal IC, please follow the
procedure following.
Replace P.W.B.
Lower
(than 15V)
Lower
(than 15V)
Power P.W.B. may malfunction.
(Replace power P.W.B.)
Normal(15V)
Normal(15V)
Internal IC is OK.
Driver IC which is in IPM may
malfunction.(Replace main P.W.B.)
RAS_25_35_AW_109-118 2003.12.31, 11:00 AM 112