Mitsubishi Heavy Industries SRK100VNXWZRF Service Manual page 38

(v) Phenomenon observed after short-circuit, wire breakage on sensor
Operation
Sensor
mode
Cooling
Room air
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
(vi) Checking the indoor electrical equipment
1) Indoor unit PCB check procedure
Is there voltage between terminal
blocks ① and ② ? (AC 220/230/240
V)
Is the fuse burnt out? (3.15 A)
Is the voltage between terminal
blocks ② and ③ oscillating between
DC 0 and 20V?
Indoor electrical components
are normal.
2) Indoor fan motor check procedure
a) Indoor unit PCB output check
i)
ii)
iii)
DC several V
(4-6 V)
CNU
Short-circuit
Freezing cycle system protection trips and stops the compressor.
Control input circuit resding
Shortcircuit
NO
YES
YES
NO
NO
YES
(–)
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.
Inspect power source
for outdoor unit.
Replace fuse.
Replace indoor unit PCB.
DC 308-336V
Indoor unit PCB
② ①
37
- -
② ①
'22 • PAC-SM-422
Disconnected wire
'09•SRK-DB-087D
Disconnected wire
① ④ ⑤
Measuring Voltage range when
point normal
① − ③
④ − ③
⑤ − ③
-
-