Specifications
175
● Inspection of resistance value of discharge-
pipe thermistor.
Remove the connector and check the resistance value.
See the section of thermistor characteristics on page 170.
● Inspection of electronic expansion valve
To test if there is voltage.
(Voltage is only applied to the electronic expansion valve when the valve angle is
being changed.)
Red to white
Red to Orange
Brown to yellow
Brown to blue
If the expansion valve does not operate as shown above, it is defective.
Normal if there is approximately DC 5 V 10 seconds
after the power supply is turned on.
}
● Display lamp inspection
• LED 5 (Abnormality display lamp - Red)
• LED 1 to 3: (Light display for each room -
Green)
ON or flashing: Protection function operating)
ON when there is a serial signal being
received among each of the indoor units.
OFF during ignition, stop (including no
connection), abnormality
*
Tester probe
∞
Normal
condition
,
+ (RD)
+ (RD)
~ (OR)
~ (GR)
.
+ (OR)
+ (GR)
– (BK)
– (BK)
(When tester probes
are inverted, the read-
ing should be approx.
10~20Ω.)
● Inspection of diode stack (DS1)
Tester probe
∞
Normal
condition
,
+ (BL)
+ (BL)
.
~ (RD)
~ (RD)
(When tester probes
are inverted, the read-
ing should be approx.
10~20Ω.)
● Inspection of diode stack (DS2)
. mark
Tester probe
(BK)
Tester probe
(RD)
● Inspection of capacitor
Check the charging characteristics
with a tester. (Needle should
swing and return slowly. Change
the polarity and check again. If
the needle returns, it is normal.)
● Power supply and serial
signal inspection
1 to 2: AC220/240V
2 to 3: Normal if the voltage oscil-
lates between DC 0 and
approx. 12V
● Inspection of reactor conductivity
Remove the connector and check for conductivi-
ty. It must be conductive.
● Inspect power transistor.
Remove the fasten terminal and test out-
put voltage.
*
Notes (1) This illustration shows SCM68ZA, however, the check procedure is the same.
FM
O
20S
Power source
1 Phase
220/230/240V 50Hz
Unit
A
Unit
B
Unit
C
L
1
2
3
1
2
3
1
2
3
Fuse
250V 25A
CT
PCB (POWER)
BK BK
WH
RD
PK
BL
WH
R
1
P
1
N
1
S
1
DS
1
DS
2
Re
CM
C
S
2
R
4
G
GR
OR Y
11
22
RD
BK
BL
+
–
+
–
P
N
W
V
U
RD
Power transistor
BK
P
2
+
N
2
WH
BL
S-A S-B S-C COM
1
CNB CNC
CNNCNMCND
CNF
Th
O-A
Th
O-R
Th
O-D
Y/
GN
Y/
GN
N
NF
PCB (POWER TRANSISTOR)
PCB (CONTROL)
EEV
A
FM
O
20S
EEV
B
EEV
C
52X
5-1
R12
SA
Y
Y
Y
BL
WH
CNN CNLCNKCNMCND
CNLCNK
LED
1
A
LED
5
ERROR
LED
3
C
LED
2
B
CNS CNT CNU
Check fuse. There should be conductivity.
Approx. DC 280 V
(b) Outdoor unit inspection points
u * Check these points with the power
supply on.
CAUTION – HIGH VOLTAGE
High voltage is produced in the control box. Don't touch
electrical parts in the control box for 5 minutes after the
unit is stopped.