Mitsubishi Electric EHST20C-VM6HB Service Manual page 30

<Abnormalities detected while unit is operating>
Abnormal point and detection method
Check code
High pressure (High-pressure switch
63H operated)
Abnormal if high-pressure switch 63H
operated (4.15 MPa) during compressor
operation.
63H: High-pressure switch
U1
High discharge temperature
(1) Abnormal if discharge temperature
thermistor (TH4) exceeds 125: or
110: continuously for 5 minutes.
Abnormal if discharge temperature
thermistor (TH4) exceeds 110: or
more continuously for 30 seconds after
90 seconds have passed since the
defrosting operation started.
(2) Abnormal if discharge superheat
(Cooling: TH4−T
Heating: TH4−T
continuously for 10 minutes.
U2
High comp. surface temperature
Abnormal if comp. surface temperature
(TH34) exceeds 125:. In the case of
high comp. surface temperature error,
compressor does not restart unless the
thermistor (TH34) becomes less than
95:.
Open/short circuit of discharge
temperature thermistor (TH4) / Comp.
surface temperature thermistor (TH34)
Abnormal if open (3: or less) or short
(217: or more) is detected during
compressor operation.
U3
(Detection is inoperative for 10 minutes
of compressor starting process and for 10
minutes after and during defrosting.)
OCH533D
1 Defective operation of stop
valve (Not fully open)
2 Clogged or broken pipe
3 Locked outdoor fan motor
4 Malfunction of outdoor fan
motor
5 Short cycle of outdoor unit
6 Dirt of outdoor heat exchanger
7 Decreased airflow caused by
defective inspection of outside
temperature thermistor
(It detects lower temperature
than actual temperature.)
8 Disconnection or contact failure
of connector (63H) on outdoor
controller board
9 Disconnection or contact failure
of 63H connection
0 Defective outdoor controller
board
1 Defective action of linear
expansion valve
2 Malfunction of fan driving circuit
1 Overheated compressor
operation caused by shortage
of refrigerant
2 Defective operation of stop
valve
3 Defective thermistor
4 Defective outdoor controller
board
5 Defective action of linear
expansion valve
/
6 Clogging with foreign objects in
63HS
) exceeds 70: refrigerant circuit
63HS
Note: Clogging occur in the parts
1 Disconnection or contact failure
of connector (TH4/TH34) on
the outdoor controller circuit
board
2 Defective thermistor
3 Defective outdoor controller
circuit board
Case
1 Check if stop valve is fully open.
2 Check piping and repair defect.
3–6 Check outdoor unit and repair defect.
7 Check the detected temperature of outside
8–0 Turn the power off and check F5 is
1 Check linear expansion valve.
2 Replace outdoor controller board.
1 Check intake superheat.
2 Check if stop valve is fully open.
34 Turn the power off and check if U3 is
5 Check linear expansion valve.
6 After recovering refrigerant, remove water
which become below
freezing point when water
enters in refrigerant circuit.
1 Check connection of connector (TH4/TH34)
2 Check resistance value of thermistor (TH4/
3 Replace outdoor controller board.
30
Judgment and action
temperature thermistor on LED display.
(SW2 on A-Control Service Tool : Refer to
"11-7. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
displayed when the power is turned again.
When F5 is displayed, refer to "Judgment
and action" for F5.
Refer to "11-4. HOW TO CHECK THE
PARTS".
Check leakage of refrigerant.
Charge additional refrigerant.
displayed when the power is turned on again.
When U3 is displayed, refer to "Judgment
and action" for U3.
Refer to "11-4. HOW TO CHECK THE
PARTS".
from entire refrigerant circuit under vacuum
more than 1 hour.
on the outdoor controller circuit board.
Check breaking of the lead wire for
thermistor (TH4/TH34). Refer to "11-6. TEST
POINT DIAGRAM".
TH34) or temperature by microprocessor.
(Thermistor/TH4/TH34: Refer to "11-4. HOW
TO CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer to "11-7.
FUNCTION OF SWITCHES, CONNECTORS
AND JUMPERS". )