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Troubleshooting for MSP Duct Type Indoor Unit
SiSG121917E
133
Part 6 Service Diagnosis
Reference
6.6 Thermistor or Related Abnormality
Error Code
C4
,
C5
,
C9
Method of Error
Detection
The temperatures detected by the thermistors determine thermistor errors.
Error Decision
Conditions
The voltage between the both ends of the thermistor is either 4.96 V or more, or 0.04 V or less
with the power on.
Supposed
Causes
Disconnection of connector
Defective thermistor(s)
Defective indoor unit PCB
Troubleshooting
If the cause of the problem is related to the thermistors, the thermistors should be checked prior
to changing the indoor unit PCB.
To check the thermistors, proceed as follows:
1. Disconnect the thermistor from the indoor unit PCB.
2. Read the temperature and the resistance value.
3. Check if the measured values correspond with the values in the table of thermistor
resistance check.
C4
: Indoor heat exchanger thermistor 1 (liquid pipe) (R2T)
C5
: Indoor heat exchanger thermistor 2 (R3T)
C9
: Room temperature thermistor (R1T)
Check No.01
Refer to P.169
YES
(R21
8
70)
N
O
Check No. 01
Check the thermistor resistance
v
al
u
e.
YES
N
O
Caution
Correct the connection.
Replace the defecti
v
e
thermistor.
Replace the indoor
u
nit PCB
(control PCB).
N
ormal?
N
ormal?
Check the connection of
connectors.
Be s
u
re to t
u
rn off the po
w
er s
w
itch
b
efore connecting or disconnecting
connectors, or parts may
b
e damaged.