Self-Diagnosis Action Table - Mitsubishi Electric PAA-A18AA1 Service Manual

13.3. Self-diagnosis action table

Error Abnormal point and detection method
Code
P1 Room temperature thermistor (TH1)
(5101)
1. The unit is in three-minute resume prevention mode if short/
open of thermistor is detected. Abnormal if the unit does
not reset normally after three minutes. (The unit returns to
normal operation, if it has normally reset.)
2. Constantly detected during cooling, drying and heating oper-
ation Short: 90˚ C [194˚ F] or more Open: -40˚ C [-40˚ F] or
less
P2 Pipe temperature thermistor/Liquid (TH2)
(5102)
1. The unit is in three-minute resume prevention mode if short/
open of thermistor is detected. Abnormal if the unit does
not reset normally after three minutes. (The unit returns to
normal operation, if it has normally reset.)
2. Constantly detected during cooling, drying, and heating (ex-
cept defrosting) operation. Short: 90˚ C [194˚ F] or more
Open: -40˚ C [-40˚ F] or less
P4 Contact failure of drain float switch (CN4F)
(2502)
1. Extract when the connector of drain float switch is discon-
nected. (3 and 4 of connector CN4F is not short-circuited.)
2. Constantly detected during operation.
P6 Freezing/overheating protection is working
(1501)
1. Freezing protection (Cooling mode) The unit is in six-minute
resume prevention mode if pipe <liquid or condenser/evap-
orator> temperature stays under -15˚ C [5˚ F] for three
minutes after the compressor started. Abnormal if it stays
under -15˚ C [5˚ F] for three minutes again within 16 minutes
after six-minute resume prevention mode.
2. Overheating protection (Heating mode) The units are in
six-minute resume prevention mode if pipe < Liquid or
condenser / evaporator > temperature is detected as over
70˚ C [158˚ F] after the compressor started. Abnormal if the
Specifications are subject to change without notice.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1 and all-
1.
2.
3.
4.
1.
2.
3.
4.
5.
1.
2.
(Cooling or drying mode)
1.
2.
3.
4.
46
Cause
Defective thermistor char- 1–3. Check resistance value of thermistor.
acteristics
0˚ C [32˚ F].......15.0kΩ
Contact failure of connector
10˚ C [50˚ F].....9.6kΩ
(CN20) on the indoor con-
20˚ C [68˚ F].....6.3kΩ
troller board (Insert failure)
30˚ C [86˚ F].....4.3kΩ
Breaking of wire or contact
40˚ C [104˚ F]...3.0kΩ
failure of thermistor wiring
If you put force on (draw or bend) the lead wire
Defective indoor controller
with measuring resistance value of thermistor
board
breaking of wire or contact failure can be detec-
ted.
2. Check contact failure of connector (CN20) on
the indoor controller board. Refer to Test Point
Diagram. Turn the power on again and check
restart after inserting connector again.
4. Check room temperature display on remote
controller. Replace indoor controller board if
there is abnormal difference with actual room
temperature.
Turn the power off, and on again to operate after
check.
Defective thermistor char- 1–3. Check resistance value of thermistor. For
acteristics characteristics, refer to (P1) above.
Contact failure of connector 2. Check contact failure of connector (CN44) on
(CN44) on the indoor con- the indoor controller board. Refer to Test Point
troller board (Insert failure) Diagram. Turn the power on again and check
restart after inserting connector again.
Breaking of wire or contact
failure of thermistor wiring 4. Check pipe <liquid> temperature with remote
controller in test run mode. If pipe<liquid> tem-
Defective refrigerant circuit
perature is extremely low (in cooling mode) or
is causing thermistor tem-
high (in heating mode), refrigerant circuit may
perature of 90˚ C [194˚ F]
have defective.
or more or -40˚ C [-40˚ F]
or less. 5. Check pipe <liquid> temperature with remote
controller in test run mode. If there is extreme
Defective indoor controller
difference with actual pipe <liquid> temperature,
board.
replace indoor controller board. Turn the power
off, and on again to operate after check.
Contact failure of connector 1. Check contact failure of float switch con-
(Insert failure) nector. Turn the power on again and check
after inserting connector again.
Defective indoor controller
board 2. Operate with connector (CN4F) short-
circuited. Refer Test Point Diagram. Re-
place indoor controller board if abnormality
reappears.
(Cooling or drying mode)
1. Check clogging of the filter
Clogged filter (reduced air-
2. Remove shields
flow)
4. Check outdoor fan motor
Short cycle of air path
5~6. Check operating condition of refrigerant
Low-load (low temperature)
circuit.
operation beyond the toler-
(Heating mode)
ance range
1. Check clogs of the filter
Defective furnace fan mo-
2. Remove shields
tor
4. Check outdoor fan motor
• Fan motor is defective.
5~7. Check operating condition of refrigerant
• Indoor controller board is
circuit
defective.
Countermeasure
© 2022 Mitsubishi Electric US, Inc.