Mitsubishi Electric TRANE NTXAMT12A112AA Service Manual page 47

Error Abnormal point and detection method
Code
P8 Pipe temperature
<Cooling mode>
Detected as abnormal when the pipe temperature is not in the
cooling range 3 minutes after compressor start and 6 minutes
after the liquid or condenser/evaporator pipe is out of cooling
range.
NOTE
1) It takes at least 9 minutes. to
detect.
2) Abnormality P8 is not detected in
drying mode.
Cooling range : -3˚C(-5.4˚F) ] (TH-TH1)
TH: Lower temperature between: liquid pipe temperature (TH2)
and condenser/evaporator temperature (TH5)
TH1: Intake temperature
<Heating mode>
When 10 seconds have passed after the compressor starts
operation and the hot adjustment mode has finished, the unit is
detected as abnormal when condenser/evaporator pipe temper-
ature is not in heating range within 20 minutes.
NOTE
3) It takes at least 27 minutes to
detect abnormality.
4) It excludes the period of de-
frosting (Detection restarts when
defrosting mode is over)
Heating range : 3˚C(5.4˚F) [ (TH5-TH1)
P9 Abnormality of pipe temperature thermistor / Condenser-Evapo-
rator (TH5)
1. The unit is in three-minute resume protection mode if
short/open of thermistor is detected. Abnormal if the unit
does not get back to normal within three minutes. (The
unit returns to normal operation, if it has normally reset.)
2. 2 Constantly detected during cooling, drying, and heating
operation (except defrosting) Short: 90˚C[194˚F] or more
Open: -40˚C[-40˚F] or less
Specifications are subject to change without notice.
NTXAMT12, 18, 24, 30, 36A112AA
Cause
1. Slight temperature difference
between indoor room temper-
ature and pipe <liquid or con-
denser / evaporator> tempera-
ture thermistor
• Shortage of refrigerant
• Disconnected holder of pipe
<liquid or condenser / evapora-
tor> thermistor
• Defective refrigerant circuit
2. Converse connection of exten-
sion pipe (on plural units con-
nection)
3. Converse wiring of indoor/ out-
door unit connecting wire (on
plural units connection)
4. Defective detection of indoor
room temperature and pipe
<condenser / evaporator> tem-
perature thermistor
5. Stop valve is not opened com-
pletely
1. Defective thermistor character-
istics
2. Contact failure of connector
(CN44) on the indoor controller
board (Insert failure)
3. Breaking of wire or contact fail-
ure of thermistor wiring
4. Temperature of thermistor
is 90:[194˚F] or more or
-40˚C[-40˚F] or less caused by
defective refrigerant circuit
5. Defective indoor controller
board
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Countermeasure
1~4. Check pipe <liquid or condenser / evapo-
rator> temperature with room temperature dis-
play on remote controller and outdoor control-
ler circuit board.
Conduct temperature check
with outdoor controller circuit
board after connecting 'A-
Control Service Tool(PAC-
SK52ST)'.
2~3. Check converse connection of extension
pipe or converse wiring of indoor/outdoor unit
connecting wire.
1–3. Check resistance value of thermistor. For
characteristics, refer to (P1) above.
2. Check contact failure of connector (CN44)
on the indoor controller board. Refer to 12-5.
Turn the power on and check restart after
inserting connector again.
4. Operate in test run mode and check pipe
<condenser / evaporator>temperature. If pipe
<condenser / evaporator> temperature is ex-
tremely low (in cooling mode) or high (in heat-
ing mode), refrigerant circuit may have defect.
5. When no problems are found in 1–4 above,
replace the indoor unit control board.