Mitsubishi Electric PAA-A18AA1 Service Manual page 46

Error Abnormal point and detection method
Code
P8 Pipe temperature
(1503) <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 de-
tect.
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 tempera-
ture 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 defrosting
(Detection restarts when defrosting
mode is over)
Heating range: 3˚ C (5.4˚ F) [ (TH5-TH1)
P9 Abnormality of pipe temperature thermistor / Condenser-Evapora-
tor (TH5)
(5105)
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.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Cause
1. Slight temperature differ-
ence between indoor room
temperature and pipe <liq-
uid or condenser / evapora-
tor> temperature thermistor
• Shortage of refrigerant
• Disconnected holder of
pipe < liquid or condenser /
evaporator > thermistor
• Defective refrigerant cir-
cuit
2. Converse connection of ex-
tension pipe (on plural units
connection)
3. Converse wiring of indoor/
outdoor unit connecting
wire (on plural units con-
nection)
4. Defective detection of in-
door return air temperature
and pipe < condenser /
evaporator > temperature
thermistor
5. Stop valve is not opened
completely
1. Defective thermistor char-
acteristics
2. Contact failure of connector
(CN44) on the indoor con-
troller board (Insert failure)
3. Breaking of wire or contact
failure of thermistor wiring
4. Temperature of thermistor
is 90˚ C [194˚ F] or more
or -40˚ C [-40˚ F] or less
caused by defective refrig-
erant circuit
5. Defective indoor controller
board
46
Countermeasure
1~4. Check pipe <liquid or condenser / evapo-
rator> temperature with return air temperature
display 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 Test Point
Diagram. 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 heating
mode), refrigerant circuit may have defect.
5. When no problems are found in 1–4 above,
replace the indoor unit control board.
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