Simple Check Method For Main Components; Checking The Outdoor Thermistors; Checking The Reversing Valve Coil; Cooling Operation Works When Heating Is Expected - Mitsubishi Electric MXZ-18NV Service Manual

(Simple check method for main components)

F Checking the outdoor thermistors
Outdoor thermistor abnormality
MXZ-18NV
Disconnect the connectors CN641, CN661 and CN681,CN682,CN683 from the outdoor controller.
MXZ-32NV
Disconnect the connectors CN661, CN662 and CN663 from the outdoor controller.
(Check the characteristic of thermistors.)
Measure the resis-
tance between
pin3 and pin4 at
CN641(MXZ-18NV)
pin1 and pin2 at
Defrost
CN661(MXZ-32NV)
thermistor
Measure the resis-
tance between
pin3 and pin4 at
Discharge
CN661(MXZ-18NV)
temperature
pin1 and pin2 at
thermistor
CN661(MXZ-32NV).
Measure the resis-
tance between
pin1and pin2, 3
and 4, 5 and 6, and
Gas pipe
at CN662 respec-
temperature
tively (MXZ-18NV)
thermistor
pin1 and pin2 at
CN661 (MXZ-32NV).
Measure the resis-
tance between pins
Suction
5 and 6 at CN661,
Evaporation
and pins 7 and 8
temperature
at CN662 respec-
thermistors
tively (MXZ-18NV)
pin1 and pin2 at
CN661 (MXZ-32NV).
Measure the
Fin
resistance
temperature
between pin1
thermistor
and pin2 at
CN663 (MXZ-18NV)
pin1 and pin2 at
CN661 (MXZ-32NV).
G Checking the reversing valve coil

Cooling operation works when heating is expected.

• First, measure the resistance of the reversing valve coil to check the integrity.
• If connector CN61(MXZ-18NV), CN913(MXZ-32NV) is not connected or the reversing valve coil is open, voltage
occurs between terminals even when the control is OFF.
Disconnect the lead wire
between compressor and
IPM board.
Turn on power to the indoor
unit and the outdoor unit,
and press the emergency
switch for heating operation.
46
As per the Chara-
Yes
cteristic Chart?
(See page 49, 51 .)
No
Thermistor damaged
No
As per the Chara-
cteristic Chart?
Yes
(See page 49, 51 .)
As per the Chara-
Yes
cteristic Chart?
(See page 49, 51 .)
No
Thermistor damaged
No
As per the Chara-
cteristic Chart?
(See page 49, 51 .)
Yes
MXZ-18NV
Three minutes after
power-on. Check the
voltage between pin1
and pin2 at CN61 on
the electronic control
P.C. board. Is there
voltage of 220 to 240V AC?
MXZ-32NV
Three minutes after
power-on. Check the
voltage between pin1
and pin2 at CN913 on
the noise filter board.
Is there voltage of 220 to
240V AC ?
1 Connect the connections CN661, CN681, CN682, CN683
CN641 (MXZ-18NV),CN661, CN662, and CN663 (MXZ-32NV).
2 Disconnect the compressor lead wire.
Turn on POWER to the
Defrost
indoor and outdoor unit
Thermistor
Is there voltage of 2.5
to 4.0V DC across
R641(MXZ-18NV),
R642(MXZ-32NV)?
Discharge
thermistor
Measure the Is there voltage of
0.3 to 0.6VDC across
voltage between
R685(MXZ-18NV),
terminals on the
R652(MXZ-32NV) at
outdoor controller
11; to 36; of
board.
outside temperature?
Evaporator/ suction
temperature thermistor.
Is there voltage of
2.5 to 4.0V DC between
terminals of R681 and R682 ?
Fin temperature thermistor.
Is there voltage of
0.8 to 2.5V DC between
terminals of R661 ?
Gas pipe temperatore thermistor
Is there voltage of
2.5 to 4.0V DC between
terminals of R683 and R684 ?
No
Yes
Yes
No
No
Disconnect the
connector
(Poor connection.)
Yes
Outdoor controller
Yes
board defective
No
No
Yes
No
Yes
Outdoor controller board
or noise electronic control
P.C. board detective.
• Reversing valve coil
lead wire defective.
• Poor contact of
connector.
• Reversing valve coil
damaged.
Outdoor controller board
or noise filter board
detective.