Mitsubishi Electric EHST20C-VM6HB Service Manual page 66

Indication
Outdoor controller board
LED1 (Green) LED2 (Red)
3 blinking 1 blinking
Abnormality of comp. surface
thermistor(TH34) and discharging
temperature (TH4)
Abnormality of superheat due
to low discharge temperature
2 blinking Abnormal high pressure (High
pressure switch 63H operated.)
Abnormal low pressure (Low
pressure switch 63L operated.)
3 blinking
Abnormality of outdoor fan
motor rotational speed
Protection from overheat operation(TH3)
Compressor overcurrent
4 blinking
breaking(Startup locked)
Compressor overcurrent breaking
Abnormality of current sensor (P.B.)
Abnormality of power module
Open/short of discharge thermistor (TH4)
5 blinking
and comp. surface thermistor (TH34)
Open/short of outdoor thermistors
(TH3, TH6, TH7 and TH8)
6 blinking Abnormality of heat sink
temperature
7 blinking
Abnormality of voltage
4 blinking 1 blinking
Abnormality of room temperature thermistor (TH1)
Abnormality of pipe temperature thermistor /Liquid (TH2)
Abnormality of pipe temperature
thermistor/Condenser-Evaporator
Abnormality of drain sensor (DS)
2 blinking
Float switch(FS) connector open
Indoor drain overflow protection
3 blinking
Freezing (cooling)/overheating
(heating) protection
Abnormality of pipe
4 blinking
temperature
*1 Check code displayed on remote controller
*2 Refer to service manual for indoor unit.
OCH533D
Check
Contents
code
*1
U2
1Check if stop valves are open.
2Check if connectors (TH4, TH34, LEV-A, and LEV-B) on outdoor controller
board are not disconnected.
3Check if unit is filled with specified amount of refrigerant.
4Measure resistance values among terminals on indoor valve and
U7
outdoor linear expansion valve using a tester.
U1 1Check if outdoor units have a short cycle on their air ducts.
2Check if connector (63H/63L) on outdoor controller board is not disconnected.
3Check if heat exchanger and filter is not dirty.
4Measure resistance values among terminals on linear expansion valve
UL
using a tester.
U8
1Check the outdoor fan motor.
2Check if connector (TH3) on outdoor controller board is disconnected.
Ud
UF 1Check if stop valves are open.
2Check looseness, disconnection, and converse connection of
compressor wiring.
3Measure resistance values among terminals on compressor using a tester.
UP
4Check if outdoor unit has a short cycle on its air duct.
UH
5Check leakage of refrigerant.
U6
U3 1Check if connectors (TH3, TH4, TH6, TH7 and TH34) on outdoor controller
board, and connector (CN3) on outdoor power board are not disconnected.
2Measure resistance value of outdoor thermistors.
U4
1Check if outdoor units have a short cycle on their air ducts.
U5
2Measure resistance value of outdoor thermistor(TH8).
U9
1Check looseness, disconnection, and converse connection of
compressor wiring.
2Measure resistance value among terminals on compressor using a tester.
3Check the continuity of contactor (52C).
4Check if power supply voltage decreases.
5Check the wiring of CN52C.
6Check the wiring of CNAF.
P1
1Check if connectors (CN20, CN21, CN29 and CN44) and terminal
blocks on indoor controller board are not disconnected.
P2
2Measure resistance value of indoor thermistors.
P9
Note: Refer to the indoor unit's Installation Manual.
P4
1Check if connector (CN31)(CN4F) and terminal blocks on indoor controller
2Measure resistance value of indoor thermistors.
3Measure resistance value among terminals on drain-up machine using a tester.
P5
4Check if drain pump works.
5Check drain function.
Note: Refer to the indoor unit's Installation Manual.
P6
1Check if indoor unit has a short cycle on its air duct.
2Check if heat exchanger and filter is not dirty.
3Measure resistance value on indoor and outdoor fan motors.
4Check if the inside of refrigerant piping is not clogged.
P8
1Check if indoor thermistors(TH2 and TH5) are not disconnected from holder.
2Check if stop valve is open.
3Check converse connection of extension pipe. (on plural units connection)
4Check if indoor/outdoor connecting wire is connected correctly.
(on plural units connection)
Error
Inspection method
board is not disconnected.
66
Detailed
reference
page
P.30
P.31
P.30
P.33
P.31
P.33
P.33
P.34
P.33
P.34
P.30
P.31
P.31
P.32,33
*2
*2
*2
*2
*2
*2