Mitsubishi Electric PEAD Series Service Manual page 39

TROUBLESHOOTING
12-3. SELF-DIAGNOSIS ACTION TABLE
Error Code Abnormal point and detection method
Room temperature thermistor (TH1)
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 operation
Short: 90°C[194˚F] or more
Open: -40°C[-40˚F] or less
P1
Pipe temperature thermistor/Liquid
(TH2)
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,
P2 drying, and heating (except defrosting)
operation.
Short: 90°C[194˚F] or more
Open: -40°C[-40˚F] or less
Contact failure of drain float switch
(CN4F)
1. Extract when the connector of drain float
P4 switch is disconnected.
(5701) (3 and 4 of connector CN4F is not
short-circuited.)
2. Constantly detected during operation.
Drain overflow protection operation
1. Suspensive abnormality, if drain float
switch is detected to be underwater for 1
minute and 30 seconds continuously with
drain pump on.
Turn off compressor and indoor fan.
2. Drain pump is abnormal if the condition
above is detected during suspensive
abnormality.
3. Constantly detected during drain pump
P5
operation.
HWE2109A
Note: Refer to the manual of outdoor unit for the details of display such as F, U, and other E.
1. Defective thermistor
characteristics
2. Contact failure of connector
(CN20) on the indoor controller
board (Insert failure)
3. Breaking of wire or contact
failure of thermistor wiring
4. Defective indoor controller
board
1. Defective thermistor
characteristics
2. Contact failure of connector
(CN44) on the indoor controller
board (Insert failure)
3. Breaking of wire or contact
failure of thermistor wiring
4. Defective refrigerant circuit is
causing thermistor temperature
of 90°C[194˚F] or more or
-40°C[-40˚F] or less.
5. Defective indoor controller
board
1. Contact failure of connector
(Insert failure)
2. Defective indoor controller
board
1. Malfunction of drain pump
2. Defective drain
Clogged drain pump
Clogged drain pipe
3. Defective drain float switch
Catch of drain float switch or
malfunction of moving parts
cause drain float switch to be
detected under water (Switch
On)
4. Defective indoor-controller
board
39
Cause
1– 3. Check resistance value of thermistor.
0°C[32˚F].......15.0kΩ
10°C[50˚F].....9.6kΩ
20°C[68˚F].....6.3kΩ
30°C[86˚F].....4.3kΩ
40°C[104˚F]...3.0kΩ
If you put force on (draw or bend) the lead
wire with measuring resistance value of
thermistor breaking of wire or contact failure
can be detected.
2. Check contact failure of connector (CN20)
on the indoor controller board. Refer to
12-5. 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.
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 again and check
restart after inserting connector again.
4. Check pipe <liquid> temperature with
remote controller in test run mode. If pipe
<liquid> temperature is extremely low (in
cooling mode) or high (in heating mode),
refrigerant circuit may have defective.
5. Check pipe <liquid> temperature with
remote controller in test run mode. If there
is extreme difference with actual pipe
<liquid> temperature, replace indoor
controller board.
Turn the power off, and on again to operate
after check.
1. Check contact failure of float switch
connector.
Turn the power on again and check after
inserting connector again.
2. Operate with connector (CN4F) short-
circuited.
Replace indoor controller board if
abnormality reappears.
1. Check if drain-up machine works.
2. Check drain function.
3. Remove drain float switch connector CN4F
and check if it is short (Switch On) with the
moving part of float switch UP, or OPEN
with the moving part of float switch down.
Replace float switch if it is short with the
moving part of float switch down.
4. Replace indoor controller board if it is
short-circuited between 3-4 of the drain float
switch connector CN4F and abnormality
reappears.
It is not abnormal if there is no problem about
the above-mentioned 1~4.
Turn the power off, and on again to operate
after check.
Countermeasure