Mitsubishi Electric Mr. Slim PUZ-M200YKA2.UK Service Manual page 34

Check Code Abnormal points and detection method
Overheat protection
Abnormal if outdoor pipe thermistor (TH3)
detects 70°C or more during compressor
operation.
Ud
(UD)*
(1504)
Compressor overcurrent interruption
(When compressor locked)
Abnormal if overcurrent of DC bus or
compressor is detected within 30 seconds
after compressor starts operating.
UF
(4100)
Current sensor error or input current error
Abnormal of 38 A of input current is detected,
or 34 A or more of input current is detected
UH
for 10 seconds continuously.
(5300)
Low pressure
Abnormal if the following conditions are
detected for continuously 3 minutes after
compressor starts heating operating for 10
minutes.
TH7−TH3 ≤ 4°C and
TH5−Indoor room temperature ≤ 2°C
UL
(1300)
Thermistor TH3: Outdoor liquid pipe temperature
TH5: Indoor cond./eva. temperature
TH7: Ambient temperature
Compressor overcurrent interruption
Abnormal if overcurrent DC bus or compres-
sor is detected after compressor starts oper-
ating for 30 seconds.
UP
(4210)
OCH775B
Cause
Defective outdoor fan (fan motor)
or short cycle of outdoor unit
during cooling operation
Defective outdoor pipe thermistor
(TH3)
Defective outdoor controller board
Stop valve is closed.
Decrease of power supply voltage
Looseness, disconnection or con-
verse of compressor wiring con-
nection
Defective compressor
Defective outdoor power board
DIP switch setting difference of
outdoor controller circuit board
Disconnection of compressor
wiring
Defective circuit of current sensor
on outdoor power circuit board
Decrease of power supply voltage
Stop valve of outdoor unit is
closed during operation.
Leakage or shortage of refrigerant
Malfunction of linear expansion
valve
Clogging with foreign objects in
refrigerant circuit
Note: If water enters in refrigerant
circuit, clogging may occur
where the part becomes
below freezing point.
Stop valve of outdoor unit is
closed.
Decrease of power supply voltage
Looseness, disconnection or con-
verse of compressor wiring con-
nection
Defective fan of indoor/outdoor
units
Short cycle of indoor/outdoor units
Defective input circuit of outdoor
controller board
Defective compressor
Defective outdoor power circuit board
DIP switch setting difference of
outdoor controller circuit board
34
Judgment and action
Check outdoor unit air passage.
Turn the power off and on again to check
the check code. If U4 is displayed, follow
the U4 processing direction.
*The check code in the parenthesis indicates
PAR-4xMAA model ("x" represents 0 or
later).
Open stop valve.
Check facility of power supply.
Correct the wiring (U V W phase) to
• •
compressor. Refer to "10-8. TEST POINT
DIAGRAM" (Outdoor power circuit board).
Check compressor.
Refer to "10-5. HOW TO CHECK THE
PARTS".
Replace outdoor power circuit board.
Check the DIP switch setting of outdoor
controller circuit board. Refer to "Model
Select" in "(1) Function of switches"
in "10-9. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".
Correct the wiring (U V W phase) to
• •
compressor. Refer to "10-8. TEST POINT
DIAGRAM" (Outdoor power circuit board).
Replace outdoor power circuit board.
Check the facility of power supply.
Check stop valve.
Check intake superheat.
Check leakage of refrigerant.
Check additional refrigerant.
Check linear expansion valve.
Refer to "10-5. HOW TO CHECK THE
PARTS".
After recovering refrigerant, remove water
from entire refrigerant circuit under vacu-
um more than 1 hour.
Open stop valve.
Check facility of power supply.
Correct the wiring (U V W phase) to com-
• •
pressor. Refer to "10-8. TEST POINT
DIAGRAM". (Outdoor power circuit board).
Check indoor/outdoor fan.
Solve short cycle.
Replace outdoor controller circuit board.
Check compressor. Refer to "10-5. HOW
TO CHECK THE PARTS".
Before the replacement of the outdoor controller
circuit board, disconnect the wiring to compressor
from the outdoor power circuit board and check the
output voltage among phases, U, V, W, during test
run. No defect on board if voltage among phases
(U-V, V-W and W-U) is same. Make sure to perform
the voltage check with same performing frequency.
Replace outdoor power circuit board
Check the DIP switch setting of outdoor
controller circuit board