Mitsubishi Electric PUHZ-W85VHA Service Manual page 15

Abnormal point and detection method
Error Code
Open/short of outdoor unit thermistors
(TH3, TH32, TH6, TH7, and TH8)
Abnormal if open or short is detected
during compressor operation.
Open detection of thermistors TH3, TH32
and TH6 is not detected for 10 seconds to
10 minutes after compressor starting and
10 minutes after and during defrosting.
Check which unit has abnormality in its
thermistor by switching the mode of
SW2.
(Refer to 8-7.)
U4
Symbol
TH3 Thermistor <Liquid temperature>
Thermistor <Inlet water temperature>
TH32
TH6 Thermistor <Plate HEX liquid temperature>
Thermistor <Ambient temperature>
TH7
TH8 Thermistor <Heatsink temperature>
Temperature of heatsink
Abnormal if heatsink thermistor (TH8)
detects 77:.
U5
Power module
Check abnormality by driving power module
in case overcurrent is detected.
(UF or UP error condition)
U6
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is
continuously detected -15: or less for
3 minutes even though linear expansion
U7
valve has minimum open pulse after com-
pressor starts operating for 10 minutes.
Case
1 Disconnection or contact failure
of connectors
( Outdoor controller circuit
board: TH3, TH32, TH6/TH7
Outdoor power circuit board:
CN3
2 Defective thermistor
3 Defective outdoor controller
circuit board
Thermistors
Name
1 The outdoor fan motor is
locked.
2 Failure of outdoor fan motor
3 Air flow path is clogged.
4 Ambient temperature is high.
5 Defective thermistor
6 Defective input circuit of
outdoor power circuit board
7 Failure of outdoor fan drive
circuit
1 Defective outdoor power circuit
board
2 Decrease of power supply voltage
3 Loosens, disconnection or
reverse of compressor wiring
connection
4 Defective compressor
1 Disconnection or loose
connection of discharge
temperature thermistor (TH4)
2 Defective holder of discharge
temperature thermistor
3 Disconnection or loose connection
of linear expansion valve's coil
4 Disconnection or loose
connection of linear expansion
valve's connector
5 Defective linear expansion valve
15
Judgment and action
1 Check connection of connector (TH3, TH32,
TH6/TH7) on the outdoor controller circuit board.
Check connection of connector (CN3) on the
)
outdoor power circuit board.
Check the lead wire for thermistor (TH3,
TH32, TH6, TH7, TH8). Refer to 8-6.
2 Check resistance value of thermistor (TH3,
TH32, TH6, TH7, TH8) or check temperature
on LED display.
(Thermistor/TH3, TH32, TH6, TH7, TH8:
Refer to 8-5.)
(SW2: Refer to 8-7)
3 Replace outdoor controller circuit board.
Open detection Short detection
– 40 or below 90 or above
– 40 or below 102 or above
– 40 or below
90 or above
– 40 or below 90 or above
– 35 or below
102 or above
12 Check outdoor fan.
3 Check air flow path for cooling.
4 Check if there is something which causes
temperature rise around outdoor unit.
(Upper limit of ambient temperature is 46:.)
Turn off power, and on again to check if U5
is displayed within 30 minutes.
If U4 is displayed instead of U5, refer to
error code U4.
5 Check resistance value of thermistor (TH8)
or temperature by microcomputer.
(Thermistor/TH8: Refer to 8-5.)
(SW2: Refer to 8-7)
6 Replace outdoor power circuit board.
7 Replace outdoor controller circuit board.
1 Replace outdoor power circuit board.
2 Check facility of power supply.
3 Correct the wiring (U
V W phase) to
• •
compressor. Refer to 8-6 (Outdoor power
circuit board).
4 Check compressor referring to 8-4.
12 Check the installation conditions of
discharge temperature thermistor (TH4).
3 Check the coil of linear expansion valve.
Refer to 8-5.
4 Check the connection or contact of LEV-A and
LEV-B on outdoor controller circuit board.
5 Check linear expansion valve.
Refer to 8-4.