Mitsubishi Heavy Industries SRK20ZIX-S Service Manual page 86

(b) Outdoor unit
Operation
Sensor
mode
Cooling
Heat exchanger
sensor
Heating
Cooling
Ourdoor air
temperature sensor
Heating
Discharge pipe
All modes
sensor
(9) Checking the indoor electrical equipment
(a) Indoor PCB check procedure
Is there voltage between terminal
blocks and ? (AC 220/230/240
V)
YES
Is the fuse burnt out? (3.15 A)
YES
Is the voltage between terminal
blocks and oscillating between
DC 0 and 20V?
YES
Indoor electrical components
are normal.
(b) Indoor unit fan motor check procedure
This is a diagnostic procedure for determining if the indoor unit's fan motor or the indoor PCB is broken down.
1) Indoor PCB output check
a) Turn off the power.
b) Remove the front panel, then disconnect the fan motor lead wire connector.
c) Turn on the power. If the unit operates when the ON/OFF button is pressed, if trouble is detected after the voltages
in the following figure are output for approximately 30 seconds, it means that the indoor PCB is normal and the
fan motor is broken down.
If the voltages in the following figure are not output at connector pins No. ① , ④ and ⑤ , the indoor PCB has failed
and the fan motor is normal.
DC several V
(4~6 V)
CNU
2) Fan motor resistance check
Measuring point
① － ③ (Red － Black)
④ － ③ (White － Black)
Shortcircuit
System can be operated normally.
Defrosting is not performed.
System can be operated normally.
Defrosting is not operated.
Compressor overload protection is disabled.
(Can be operated.)
NO
Inspect power source
for outdoor unit.
NO
Replace fuse.
NO
Replace indoor PCB.
(–)
GND
DC15V
FM
I
Resistance when normal
20 MΩ or higher
20 MΩ or higher
-
Phenomenon
Compressor stop.
Defrosting is performed for 10 minutes at approx. 35 minutes.
Compressor stop.
Defrosting is performed for 10 minutes at approx. 35 minutes.
Compressor stop
DC 308~336V
Indoor PCB
Notes (1) Remove the fan motor and measure it without power connected to it.
Notes (2) If the measured value is below the value when the motor is normal, it means
that the fan motor is faulty.
85
-
Disconnected wire
Measuring Resistance when
point normal
① － ③
DC 308~336V
④ － ③
DC 15V
⑤ － ③
DC several V (4~6V)
⑥ － ③
DC several V (4~6V)