Mitsubishi Heavy Industries SRK20HC-S Technical Manual page 32

Serial signal transmission error
(4) Phenomenon observed after shortcircuit, wire breakage on thermistor.
(a) Indoor unit
Operation
Thermistor
mode
Cooling
Room temperature
thermistor
Heating
Cooling
Heat exchanger
thermistor
Heating
(b) Outdoor unit
Operation
Thermistor
mode
Cooling
Heat exchanger
thermistor
Heating
Cooling
Outdoor temperature
thermistor
Heating
Discharge pipe
All modes
thermistor
Does error persist after power
reset?
YES
Is there any wrong connection on
indoor/outdoor unit wiring?
YES
Is DC 0~Approx. 12V detected
between 2~3 terminals on
indoor unit terminal block?
YES
Is DC 0~Approx. 12V detected
between2~3 terminals on
outdoor unit terminal block?
YES
Is AC 220/230/240V applied
between 1~2 on the outdoor side
terminal block?
YES
Defective outdoor unit PCB
Shortcircuit
Release of continuous compressor operation command
Continuous compressor operation command is not released.
System can be operated normally.
High pressure control mode
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.)
[Wiring error including power cable, defective indoor/
outdoor unit PCB]
NO
Trouble by transient cause, not unit trouble.
NO
Correct improper wire connection on indoor/
outdoor unit.
NO
Defective indoor unit PCB
NO
Check crossover wires.
NO
Defective indoor unit PCB. Check crossover wires.
Phenomenon
Continuous compressor operation command is not released.
Release of continuous compressor operation command
Continuous compressor operation command is not released.
(Anti-frosting)
Hot keep (Indoor fan stop)
Phenomenon
System can be operated normally.
Defrosting is performed for 10 minutes at approx. 1 hour.
Defrosting is performed for 10 minutes at intervals of approx. 1 hour.
Compressor stop
30
- -
Broken wire
Broken wire