Mitsubishi Electric PCA-A24GA Service Manual page 16

Abnormal point and detection method
Error Code
Freezing/overheating protection is
working
1 Freezing protection (Cooling mode)
The unit is in 6-minute resume prevention
mode if pipe <liquid or condenser/evap-
orator> temperature stays under
-15:(5˚F) for 3 minutes, 3 minutes after
the compressor started. Abnormal if it
stays under -15:(5˚F) for 3 minutes
again within 16 minutes after 6-minute
resume prevention mode.
P6
2 Overheating protection (Heating mode)
The units is in 6-minute resume
prevention mode if pipe <condenser /
evaporator> temperature is detected as
over 70:(158˚F) after the compressor
started. Abnormal if the temperature of
over 70:(158˚F) is detected again with-
in 10 minutes after 6-minute resume
prevention mode.
Pipe temperature
<Cooling mode>
Detected as abnormal when the pipe tem-
perature is not in the cooling range 3 min-
utes 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.
Note 2) Abnormality P8 is not detected in
drying mode.
Cooling range:-3 deg C[-5.4deg F]](TH-TH1)
TH: Lower temperature between liquid pipe
temperature (TH2) and
condenser/evaporator temperature
(TH5)
P8 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 temperature is
not in heating range within 20 minutes.
Note 3) It takes at least 27 minutes to
detect abnormality.
Note 4) It excludes the period of defrosting
(Detection restarts when defrosting
mode is over)
Heating range:3 deg C[5.4deg F][(TH5-TH1)
Cause
(Cooling or drying mode)
1 Clogged filter (reduced airflow)
2 Short cycle of air path
3 Low-load (low temperature)
operation out of the tolerance
range
4 Defective indoor fan motor
• Fan motor is defective.
• Indoor controller board is
defective.
5 Defective outdoor fan control
6 Overcharge of refrigerant
7 Defective refrigerant circuit
(clogs)
(Heating mode)
1 Clogged filter (reduced airflow)
2 Short cycle of air path
3 Overload (high temperature)
operation beyond the tolerance
range
4 Defective indoor fan motor
• Fan motor is defective.
• Indoor controller board is
defective.
5 Defective outdoor fan control
6 Overcharge of refrigerant
7 Defective refrigerant circuit
(clogs)
8 Bypass circuit of outdoor unit
is defective.
1 Slight temperature difference
between indoor room
temperature and pipe <liquid
or condenser / evaporator>
temperature thermistor
• Shortage of refrigerant
• Disconnected holder of pipe
<liquid or condenser /
evaporator> thermistor
• Defective refrigerant circuit
2 Converse connection of
extension pipe (on plural units
connection)
3 Converse wiring of indoor/
outdoor unit connecting wire
(on plural units connection)
4 Defective detection of indoor
room temperature and pipe
<condenser / evaporator>
temperature thermistor
5 Stop valve is not opened
completely.
16
Countermeasure
(Cooling or drying mode)
1 Check clogs of the filter.
2 Remove shields.
4 Measure the resistance of fan motor's winding.
Measure the output voltage of fan's connector
(FAN) on the indoor controller board.
WThe indoor controller board should be
normal when voltage of AC 208/230V is
detected while fan motor is connected.
Refer to 10-6.
5 Check outdoor fan motor.
67 Check operating condition of refrigerant
circuit.
(Heating mode)
1 Check clogs of the filter.
2 Remove shields.
4 Measure the resistance of fan motor's winding.
Measure the output voltage of fan's connector
(FAN) on the indoor controller board.
WThe indoor controller board should be
normal when voltage of AC 208/230V is
detected while fan motor is connected.
Refer to 10-6.
5 Check outdoor fan motor.
6~8Check operating condition of refrigerant
circuit.
1~4 Check pipe <liquid or condenser /
evaporator> temperature with room
temperature display on remote controller
and outdoor controller circuit board.
Pipe <liquid or condenser / evaporator>
temperature display is indicated by setting
SW2 of outdoor controller circuit board as
follows.
Conduct temperature check with outdoor
(
controller circuit board after connecting
'A-Control Service Tool(PAC-SK52ST)'.
23Check converse connection of extension
pipe or converse wiring of indoor/outdoor
unit connecting wire.
)