Mitsubishi Electric ecodan PUHZ-W50VHA2, Service Manual

Page: 17 / 60

17
Check Code Abnormal point and detection method Case Judgment and action
U4
Open/short of outdoor unit thermistors
(TH3, TH6, TH32, TH34, 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.
Note: Check which unit has abnormality in
its thermistor by switching the mode of
SW2. (PAC-SK52ST) (Refer to "8-7.
OUTDOOR UNIT OPERATION
MONITOR FUNCTION".)
1
Check connection of connector (TH3, TH32,
TH34, TH6/TH7) on the outdoor controller circuit
board. Check connection of connector (CN6) on
the outdoor power circuit board. Check the lead
wire for thermistor (TH3, TH32, TH34, TH6, TH7,
TH8). Refer to "8-6. TEST POINT DIAGRAM".
2
Check resistance value of thermistor (TH3,
TH32, TH34, TH6, TH7, TH8) or check tem -
perature on LED display. (Thermistor/TH3,
TH32, TH34, TH6, TH7, TH8: Refer to "8-5.
HOW TO CHECK THE COMPONENTS".)
(SW2: Refer to "8-7. OUTDOOR UNIT
OPERATION MONITOR FUNCTION".)
3
Replace outdoor controller circuit board.
U5
Temperature of heat sink
Abnormal if heat sink thermistor (TH8)
detects temperature indicated below.
W50VHA2 ••••••••••••• 77°C
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
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 check code U4.
5
Check resistance value of thermistor (TH8) or tem -
perature by microcomputer. (Thermistor/TH8: Refer
to "8-5. HOW TO CHECK THE COMPONENTS".)
(SW2: Refer to "8-7. OUTDOOR UNIT
OPERATION MONITOR FUNCTION".)
6
Replace outdoor power circuit board.
7
Replace outdoor controller circuit board.
U6
Power module
Check abnormality by driving power module
in case overcurrent is detected.
(UF or UP error condition)
1
Defective outdoor power cir -
cuit board
2
Decrease of power supply voltage
3
Looseness, disconnection or
reverse of compressor wiring
connection
4
Defective compressor
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. TEST POINT
DIAGRAM" (Outdoor power circuit board).
4
Check compressor referring to "8-4. HOW
TO CHECK THE PARTS" .
U7
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
valve has minimum open pulse after
compressor starts operating for 10
minutes.
1
Disconnection or loose
connection of discharge
temperature thermistor (TH4)
2
Defective holder of discharge
temperature thermistor
3
Disconnection or loose connec -
tion of linear expansion valve’s
coil
4
Disconnection or loose
connection of linear expansion
valve’s connector
5
Defective linear expansion valve
12
Check the installation conditions of dis -
charge temperature thermistor (TH4).
3
Check the coil of linear expansion valve.
Refer to "8-5. HOW TO CHECK THE
COMPONENTS".
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. HOW TO CHECK THE PARTS" .
U8
Outdoor fan motor
Abnormal if rotational frequency of the fan
motor is not detected during DC fan motor
operation.
Fan motor rotational frequency is abnormal
if;
• 100 rpm or below detected continuously
for 15 seconds at 20
:
or more outside
air temperature
• 50 rpm or below or 1500 rpm or more
detected continuously for 1 minute.
1
Failure in the operation of the
DC fan motor
2
Failure in the outdoor circuit
controller board
1
Check or replace the DC fan motor.
2
Check the voltage of the outdoor circuit
controller board during operation.
3
Replace the outdoor circuit controller board.
(when the failure is still indicated even after
performing the remedy
1
above.)
( )
Thermistors
Open detection Short detection
Symbol Name
TH3 Thermistor <Liquid> −40°C or below 90°C or above
TH32 Thermistor <Inlet Water> −40°C or below 102°C or above
TH6 Thermistor <Plate HEX liquid> −40°C or below 90°C or above
TH7 Thermistor <Ambient> −40°C or below 90°C or above
TH8 Thermistor <Heat Sink> −35°C or below 102°C or above
1
Disconnection or contact failure
of connectors
Outdoor controller circuit board:
TH3, TH32, TH34, TH6/TH7
Outdoor power circuit board:
CN6
2
Defective thermistor
3
Defective outdoor controller
circuit board
OCH605A