Mitsubishi Electric PUZ-A12NKA7 Service Manual page 34

Check code Abnormal points and detection method
Open/short circuit of outdoor unit
temperature thermistor (TH4, TH33)
Abnormal if open (−4˚F [−20:] or less) or
short (422˚F [217:] or more) is detected
during compressor operation.
U3
(Detection is inoperative for 10 minutes
(5104)
of compressor starting process and for 10
minutes after and during defrosting.)
TH33: Thermistor <Comp. surface>
Open/short of outdoor unit thermistors
(TH3, TH6, TH7, TH8 and TH32 )
Abnormal if open or short is detected during
compressor operation.
Open detection of thermistors TH3 and TH6
is inoperative 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
U4
of SW2. (PAC-SK52ST) (Refer to
(TH3:5105)
"10-10. FUNCTION OF SWITCHES,
(TH6:5107)
CONNECTORS AND JUMPERS".)
(TH7:5106)
(TH8:5110)
(TH33:5133)
Thermistors
Symbol
TH3 Thermistor <Liquid>
Thermistor <2-phase pipe>
TH6
Thermistor <Ambient>
TH7
TH8 Thermistor <Heat sink>
TH32 Thermistor <Suction>
Temperature of heat sink
Abnormal if heat sink thermistor (TH8)
detects temperature indicated below.
A12, 18N ···················183˚F [84:]
A24, 30N ···················170˚F [77:]
A36, 42N ···················190˚F [83:]
U5
(4230)
Power module
Check abnormality by driving power module
in case overcurrent is detected.
(UF or UP error condition)
U6
(4250)
Outdoor fan motor
Abnormal if the rotational frequency of fan
motor is not detected during DC fan motor
operation.
Fan motor rotational frequency is abnormal if;
U8
• 1 00 rpm or below detected continuously
(4400)
for 15 seconds at 68˚F [20:] or more
outside air temperature.
• 5 0 rpm or below or 1500 rpm or more
detected continuously for 1 minute.
OCH636A
1 Disconnection or contact failure
of connectors (TH4, TH33) on
the outdoor controller circuit
board
2 Defective thermistor
3 Defective outdoor controller cir-
cuit board
1 Disconnection or contact failure
of connectors
(
Outdoor controller circuit
board: TH3,TH6/TH7, TH32
Outdoor power circuit board:
CN3
2 Defective thermistor
3 Defective outdoor controller
circuit board
Open detection
Name
−58°F [−50:] or below 194°F [ 90:] or above
−58°F [−50:] or below
−58°F [−50:] or below
−54°F [−48:] or below
−58°F [−50:] or below 194°F [ 90:] or above
1 The outdoor fan motor is
locked.
2 Failure of outdoor fan motor
3 Air flow path is clogged.
4 Rise of ambient temperature
5 Defective thermistor
6 Defective input circuit of
outdoor power circuit board
7 Failure of outdoor fan drive
circuit
1 Outdoor stop valve is closed.
2 Decrease of power supply voltage
3 Looseness, disconnection or
converse of compressor wiring
connection
4 Defective compressor
5 Defective outdoor power circuit
board
1 Failure in the operation of the
DC fan motor
2 Failure in the outdoor circuit
controller board
Case
1 Check connection of connector (TH4, TH33)
on the outdoor controller circuit board. Check
breaking of the lead wire for TH4 or TH33.
Refer to "10-9. TEST POINT DIAGRAM".
2 Check resistance value of TH4, TH33, or
temperature by microprocessor.
(Thermistor/TH4, TH33: Refer to "10-6.
HOW TO CHECK THE PARTS".) (SW2 on
A-Control Service Tool: Refer to "10-10.
FUNCTION OF SWITCHES, CONNECTORS
AND JUMPERS".)
3 Replace outdoor controller board.
1 Check connection of connector (TH3,TH6/TH7,
TH32) on the outdoor controller circuit board.
)
Check connection of connector (CN3) on the
outdoor power circuit board.
Check breaking of the lead wire for thermistor
(TH3,TH6,TH7,TH8, TH32). Refer to "10-9.
TEST POINT DIAGRAM".
2 Check resistance value of thermistor
(TH3,TH6,TH7,TH8, TH32) or check tempera-
ture by microprocessor.
(Thermistor / TH3, TH6, TH7, TH8, TH32 : Refer
to "10-6. HOW TO CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer
to "10-10. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
3 Replace outdoor controller circuit board.
Note: Emergency operation is available in case
of abnormalities of TH3, TH6, TH7 and
TH32. Refer to "10-8. EMERGENCY
Short detection
OPERATION".
194°F [ 90:] or above
194°F [ 90:] or above
216°F [102:] or above
12 Check outdoor fan.
3 Check airflow path for cooling.
4 Check if there is something which causes
temperature rise around outdoor unit.
(Upper limit of ambient temperature is 114˚F [46:].)
Turn off power, and on again to check if U5 is
displayed within 30 minutes.
If U4 is displayed instead of U5, follow the
action to be taken for U4.
5 Check resistance value of thermistor (TH8) or
temperature by microprocessor.
(Thermistor/TH8: Refer to "10-6. HOW TO
CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer
to "10-10. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".
6 Replace outdoor power circuit board.
7 Replace outdoor controller circuit board.
1 Open stop valve.
2 Check facility of power supply.
3 Correct the wiring (U·V·W phase) to
compressor. Refer to "10-9. TEST POINT
DIAGRAM" (Outdoor power circuit board).
4 Check compressor referring to "10-6. HOW
TO CHECK THE PARTS".
5 Replace outdoor power circuit board.
1 Failure in the operation of the DC fan motor
2 Failure in the outdoor circuit controller board
34
judgment and action