Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 176

SCM-HG (4 room)
(7) Inverter failure diagnosis
If the results of the diagnosis in Item (3) indicate that the inverter is defective, perform the following inspection on the inverter.
(a) Diagnosis procedure
High voltage is created inside the controller box. When performing operations other than inspecting the
voltage system, stop operation and wait until LED7 on the printed circuit board of the outdoor unit has
gone out (approx. 20 minutes) before coming in contact with the components inside the controller box.
Is LED 1 (green) on the printed
circuit board on?
Is there approximately DC 280V
NO
between
P
transistor?
Is there output at CNJ on the printed
circuit board?
Is there voltage at U, V and W of the
power transistor?
Inspect compressor.
Condenser is defective
The reactor is defective
The diode stack is defective
174
[Electrical abnormalities in outdoor unit]
NO
YES
and on the power
N
YES
NO
YES
NO
YES
NO
e Replace
NO
Is there conductivity in the reactor?
e Replace
NO
e Replace
The printed circuit board is
defective e Replace
NO
Is the fuse good?
YES
NO
Is the varistor good?
YES
NO
Is the noise filter good?
YES
The printed circuit board is
defective e Replace
The printed circuit board is
defective e Replace
The power transistor is
defective e Replace
Is condenser good?
YES
YES
Is the diode stack good?
YES
Fuse is defective e Replace
The varistor is defective
e Replace
The noise filter is defective
e Replace