Mitsubishi Electric PUHZ-W90VHA, Service Manual

Page: 14 / 45

14
Thermistors
Open detection Short detection
Symbol Name
TH3
TH6
TH7
TH8
– 40 or below
– 40 or below
– 40 or below
– 40 or below
– 35 or below
90 or above
90 or above
90 or above
102 or above
102 or above
Thermistor <Liquid temperature>
Thermistor <Inlet water temperature>
Thermistor <Plate HEX liquid temperature>
Thermistor <Ambient temperature>
Thermistor <Heatsink temperature>
TH32
Error Code
Abnormal point and detection method
Case
Judgment and action
U5
Temperature of heatsink
Abnormal if heatsink thermistor(TH8)
detects temperature indicated 77
.
The outdoor fan motor is
locked.
Failure of outdoor fan motor
Air flow path is clogged.
Ambient temperature is high.
Defective thermistor
Defective input circuit of
outdoor power circuit board
Failure of outdoor fan drive
circuit
Check outdoor fan.
Check air flow path for cooling.
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.
Check resistance value of thermistor (TH8)
or temperature by microcomputer.
(Thermistor/TH8: Refer to 8-5.)
(SW2 : Refer to 8-6)
Replace outdoor power circuit board.
Replace outdoor controller circuit board.
U4
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.)
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.
Check resistance value of thermistor
(TH3,TH32,TH6,TH7,TH8) or check tempera-
ture on LED display.
(Thermistor/TH3,TH32,TH6,TH7,TH8: Refer
to 8-5.)
(SW2 : Refer to 8-7)
Replace outdoor controller circuit board.
Disconnection or contact failure
of connectors
Outdoor controller circuit
board: TH3,TH32,TH6/TH7
Outdoor power circuit board:
CN3
Defective thermistor
Defective outdoor controller
circuit board
( )
U6
Power module
Check abnormality by driving power module
in case overcurrent is detected.
(UF or UP error condition)
Defective outdoor power circuit
board
Decrease of power supply voltage
Loosen, disconnected or
reverse of compressor wiring
connection
Defective compressor
Replace outdoor power circuit board.
Check facility of power supply.
Correct the wiring (U
•
V
•
W phase) to
compressor. Refer to 8-6 (Outdoor power
circuit board).
Check compressor referring to 8-4.