Replace Fuse - Mitsubishi Electric FDT71VNPWVH Service Manual

(8) Phenomenon observed after short-circuit, wire breakage on sensor
Operation
Sensor
mode
Cooling
Room temperature
sensor
Heating
Cooling
Heat exchanger
temperature sensor
Heating
Cooling
Humidity sensor
Heating
■ Humidity sensor operation
Failure mode
(b) Outdoor unit
①
②
Operation
Sensor
mode
①②
Cooling
① ②
Heat exchanger short-
sensor
Heating
Cooling
Ourdoor air
temperature sensor
Heating
Discharge pipe
All modes
sensor
(9) Checking the indoor electrical equipment
(a) Indoor unit PCB check procedure
Is there voltage between terminal
blocks ① and ② ? (AC 220/230/240
V)
YES
Is the fuse burnt out? (3.15 A)
NO
Is the voltage between terminal
blocks ② and ③ oscillating between
DC 0 and 20V?
YES
Indoor electrical components
are normal.
(b) Indoor fan motor check procedure
This is a diagnostic procedure for determining if the indoor fan motor or the indoor unit PCB is broken down.
(i) Indoor unit PCB output check
1)
2)
3)
in the following figure are output for approximately 30 seconds, it means that the indoor unit PCB is normal and
the fan motor is broken down
failed
DC several V
(4-6 V)
CNU
Shortcircuit
Freezing cycle system protection trips and stops the compressor.
Control input circuit resding
Shortcircuit
NO
Inspect power source
for outdoor unit.
YES

Replace fuse.

NO
Replace indoor unit
PCB.
(–)
GND
DC15V
⑥ ⑤ ④ ③
⑥ ⑤ ④ ③
-
Phenomenon
Air-conditioning system operation
Phenomenon
Defrosting is performed for 10 minutes at approx. 35 minutes.
Defrosting is performed for 10 minutes at approx. 35 minutes.
DC 308-336V
Indoor unit PCB
② ①
② ①
123
-
'19 • PAC-SM-312
Disconnected wire
'09•SRK-DB-087D
Disconnected wire
① ④ ⑤
the indoor unit PCB has
Measuring Voltage range when
point normal
① − ③ −
④ − ③
⑤ − ③
−