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Mitsubishi Electric PUHZ-W85VHA Service Manual Page 14

Air to water heat pump.
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<Abnormalities detected while unit is operating>
Abnormal point and detection method
Error Code
High pressure (High-pressure switch
63H activated)
Abnormal if high-pressure switch 63H is
activated ( w ) during compressor opera-
tion.
w 4.15 MPa
63H: High-pressure switch
U1
High discharging temperature
Abnormal if discharge temperature
thermistor (TH4) exceeds 125: or 110:
continuously for 5 minutes.
Abnormal if during defrosting discharge
U2
temperature thermistor (TH4) exceeds
110: continuously for 30 minutes.
Open/short circuit of discharge
temperature thermistor (TH4)
Abnormal if open (3: or less) or short
(217: or more) is detected during
compressor operation.
U3
(Detection is inoperative for 10 seconds to
10 minutes of compressor starting process
and for 10 minutes after or during defrost-
ing.)
Case
1 Decreased water flow
2 Clogged filter of water pipe
3 Dirt of plate heat exchanger
4 Locked water pump
5 Malfunction of water pump
6 Clogged or broken pipe
7 Locked outdoor fan motor
8 Malfunction of outdoor fan
motor
9 Short cycle of outdoor unit
0 Dirt of outdoor heat exchanger
1 Decreased airflow caused by
defective inspection of outside
temperature thermistor
(It detects lower temperature
than actual temperature.)
2 Disconnection or contact failure
of connector (63H) on outdoor
controller board
3 Disconnection or contact failure
of 63H connection
4 Defective outdoor controller
board
5 Defective operation of linear
expansion valve
6 Malfunction of fan driving
circuit
1 Overheated compressor
operation caused by insufficient
refrigerant
2 Defective thermistor
3 Defective outdoor controller
board
4 Defective operation of linear
expansion valve
1 Disconnection or contact
failure of connector (TH4) on
the outdoor controller circuit
board.
2 Defective thermistor
3 Defective outdoor controller
circuit board
14
Judgment and action
1~5 Check water circuit and repair the defect.
6 Check piping and repair the defect.
7~0 Check outdoor unit and repair the defect.
1 Check the detected temperature of outside
temperature thermistor on LED display.
(SW2: Refer to 8-7.)
2~4 Turn the power off and check F5 is
displayed when the power is turned on again.
When F5 is displayed, refer to "Judgment
and action" for F5.
5 Check linear expansion valve.
Refer to 8-5.
6 Replace outdoor controller board.
1 Check intake super heat.
Check leakage of refrigerant.
Charge additional refrigerant.
23 Turn the power off and check if U3 is dis-
played when the power is turned ON again.
When U3 is displayed, refer to "Judgement
and action" for U3.
4 Check linear expansion valve.
Refer to 8-5.
1 Check connection of connector (TH4) on the
outdoor controller circuit board.
Check the lead wire for thermistor (TH4).
Refer to 8-6.
2 Check resistance value of thermistor (TH4) or
temperature on LED display.
(Thermistor/TH4: Refer to 8-5.)
(SW2: Refer to 8-7.)
3 Replace outdoor controller board.

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