Mitsubishi Electric HP120TNU-A Service Handbook page 240

Chapter 8 Troubleshooting Based on Observed Symptoms
8-1 MA Remote Controller Problems......................................................................................................... 1
8-1-1 The LCD Does Not Light Up. .................................................................................................................. 1
8-1-2 The LCD Momentarily Lights Up and Then Goes Off. ............................................................................ 2
8-1-3 "HO" and "PLEASE WAIT" Do Not Go Off the Screen. .......................................................................... 3
8-1-4 Air Conditioning Units Do Not Operate When the ON Button Is Pressed. .............................................. 4
8-2 ME remote Controller Problems .......................................................................................................... 5
8-2-1 The LCD Does Not Light Up. .................................................................................................................. 5
8-2-2 The LCD Momentarily Lights Up and Then Goes Off. ............................................................................ 6
8-2-3 "HO" or "Waiting for ···" Does Not Go Off the Screen............................................................................. 7
8-2-4 "88", "Request denied." Appears on the LCD. ........................................................................................ 9
8-3 Refrigerant Control Problems............................................................................................................ 10
8-3-1 Units in the Cooling Mode Do Not Operate at Expected Capacity........................................................ 10
8-3-2 Units in the Heating Mode Do Not Operate at Expected Capacity. ...................................................... 12
8-3-3 Outdoor Units Stop at Irregular Times. ................................................................................................. 14
8-4 Checking Transmission Waveform and for Electrical Noise Interference .................................... 15
8-4-1 M-NET................................................................................................................................................... 15
8-4-2 MA Remote Controller .......................................................................................................................... 17
8-5 Pressure Sensor Circuit Configuration and Troubleshooting Pressure Sensor Problems......... 18
8-5-1 Comparing the High-Pressure Sensor Measurement and Gauge Pressure......................................... 18
8-5-2 High-Pressure Sensor Configuration (63HS1, PS1, PS3) .................................................................... 19
8-5-3 Comparing the Low-Pressure Sensor Measurement and Gauge Pressure.......................................... 20
8-5-4 Low-Pressure Sensor Configuration (63LS) ......................................................................................... 21
8-6 Troubleshooting Solenoid Valve Problems...................................................................................... 22
8-7 Troubleshooting Outdoor Unit Fan Problems.................................................................................. 23
8-8 Troubleshooting LEV Problems ........................................................................................................ 24
8-8-1 General Overview on LEV Operation.................................................................................................... 24
8-8-2 Possible Problems and Solutions ......................................................................................................... 27
8-8-3 Coil Removal Instructions ..................................................................................................................... 28
8-9 Troubleshooting Problems with Major Components on BC Controller......................................... 30
8-9-1 Pressure Sensor ................................................................................................................................... 30
8-9-2 Temperature Sensor ............................................................................................................................. 32
8-9-3 Troubleshooting Flowchart for LEVs..................................................................................................... 36
8-9-4 Troubleshooting Flowchart for Solenoid Valves.................................................................................... 41
8-9-5 BC Controller Transformer.................................................................................................................... 43
8-10 Troubleshooting Inverter Problems .................................................................................................. 44
8-10-1 Inverter-Related Problems and Solutions ............................................................................................. 44
8-10-2 Checking the Inverter Board Error Detection Circuit............................................................................. 46
8-10-3 Checking the Compressor for Ground Fault and Coil Resistance Problems ........................................ 46
8-10-4 Checking the Inverter for Damage at No-Load ..................................................................................... 47
8-10-5 Checking the Inverter for Damage during Compressor Operation........................................................ 47
8-10-6 Checking the Fan Motor for Ground Fault and Coil Resistance Problems ........................................... 48
8-10-7 Checking the Fan Board Error Detection Circuit at No Load ................................................................ 48
8-10-8 Checking the Fan Board for Damage at No Load................................................................................. 48
8-10-9 Checking the Fan Board for Damage with Load ................................................................................... 49
8-10-10 Checking the Installation Conditions..................................................................................................... 50
8-10-11 Solutions for the Main Breaker Trip ...................................................................................................... 50
8-10-12 Solutions for the Main Earth Leakage Breaker Trip .............................................................................. 51
HWE18220_GB