Mitsubishi Heavy Industries SRK20ZIX-S Service Manual page 85

Outdoor fan motor error
Is connector connection good?
YES
* Disconnect the fan motor
connector, then investigate
the fan motor and outdoor
PCB separately.
Is the output of the outdoor PCB
normal?
YES
Normal
Rotor lock
(8) Phenomenon observed after shortcircuit, wire breakage on sensor
(a) Indoor unit
Operation
Sensor
mode
Cooling
Room temperature
sensor
Heating
Cooling
Heat exchanger
sensor
Heating
Cooling
Humidity sensor
Heating
■ Humidity sensor operation
Failure mode
① Disconnected wire
② Disconnected wire
①② Disconnected wire
① and ② are shot
circuited
Remark: Do not perform a continuity check of the humidity sensor with a tester. If DC current is applied, it
could damage the sensor.
NO
Correct connector connection
Is fan motor resistance value good?
NO
Defective outdoor PCB
Is output voltage applied to all 3
phases of power transistor?
YES
Inspect compressor.
Shortcircuit
Release of continuous compressor operation command.
Continuous compressor operation command is not released.
System can be operated normally.
High pressure control mode (Compressor stop command)
Refer to the table below.
Normal system operation is possible.
Control input circuit resding
Humidity reading is 0%
Humidity reading is 100%
NO
YES
Replace outdoor fan motor
NO
Defective outdoor PCB
¡ Check compressor wiring visually.
¡ Check insulation resistance. (1 M Ω or over)
¡ Check coil wire resistance.
Model 20~35 : 1.703 Ω or more at 20ºC
Model 50, 60 : 0.953 Ω or more at 20ºC
Phenomenon
Continuous compressor operation command is not released.
Release of continuous compressor operation command.
Continiuous compressor operation command is not released.
(Anti-frosting)
Hot keep (Indoor fan stop)
Refer to the table below.
Air conditioning system operation
Anti-condensation control is not done.
Anti-condensation control keep doing.
84
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Defective fan motor, connector poor
connection, defective outdoor PCB
Defective compressor, defective
outdoor PCB
If check results are normal,
compressor is locked.
Disconnected wire
Humidity sensor
element
Connector
(CNF)
Humidity sensor assembly