Self-Diagnosis Action Table - Mitsubishi Electric PKA-A12HA Service Manual

9-3. SELF-DIAGNOSIS ACTION TABLE

Abnormal point and detection method
Error Code
Room temperature thermistor (TH1)
The unit is in 3-minute resume
prevention mode if short/open of
thermistor is detected. Abnormal if the
unit does not reset normally after 3 min-
utes. (The unit returns to normal opera-
tion, if it has been reset normally.)
Constantly detected during cooling,
drying, and heating operation.
Short: 90
Open: -40
P1
Pipe temperature thermistor/Liquid
(TH2)
The unit is in 3-minute resume
prevention mode if short/open of
thermistor is detected. Abnormal if the
unit does not reset normally after 3 min-
utes. (The unit returns to normal opera-
tion, if it has been reset normally.)
Constantly detected during cooling,
P2
drying, and heating (except defrosting)
operation.
Short: 90
Open: -40
Contact failure of drain float switch (CN4F)
Extract when the connector of drain float
switch is disconnected.
P4
( and of connector CN4F is not
(5701)
short-circuited.)
Constantly detected during operation.
Drain overflow protection operation
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.
Drain pump is abnormal if the condition
above is detected during suspensive
abnormality.
Constantly detected during drain pump
P5
operation.
Note: Refer to the manual of outdoor unit for the details of display
such as F, U, and other E.
Cause
Defective thermistor
characteristics
Contact failure of connector
(CN20) on the indoor controller
board (Insert failure)
Breaking of wire or contact
failure of thermistor wiring
Defective indoor controller
board
Defective thermistor
characteristics
Contact failure of connector
(CN44) on the indoor controller
board (Insert failure)
Breaking of wire or contact
failure of thermistor wiring
Defective refrigerant circuit is
causing thermistor tempera-
ture of 90
-40
Defective indoor controller
board
Contact failure of connector
(Insert failure)
Defective indoor controller
board
Malfunction of drain pump
Defective drain
Clogged drain pump
Clogged drain pipe
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)
Defective indoor-controller
board
16
Countermeasure
– Check resistance value of thermistor.
0 15.0k
• • • • • • • • • •
10 9.6k
• • • • • • • • • • • •
20 6.3k
• • • • • • • • • • • •
30 4.3k
• • • • • • • • • • • •
40 3.0k
• • • • • • • • • • •
If you put force on (draw or bend) the lead wire
while measuring resistance value of thermistor,
breaking of wire or contact failure can be
detected.
Check contact failure of connector (CN20) on
the indoor controller board. Refer to 9-7.
Turn the power on again and check restart
after inserting connector again.
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.
– Check resistance value of thermistor.
For characteristics, refer to (P1) above.
Check contact failure of connector (CN44) on
the indoor controller board. Refer to 9-7.
Turn the power on and check restart after
inserting connector again.
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 defect.
Check pipe <liquid> temperature with remote
controller in test run mode. If there is extremely
difference with actual pipe <liquid> temperature,
replace indoor controller board.
Turn the power off, and on again to operate
after check.
Check contact failure of float switch connec-
tor.
Turn the power on again and check after
inserting connector again.
Operate with connector (CN4F) short-circuited.
Replace indoor controller board if abnormality
reappears.
Check if drain-up machine works.
Check drain function.
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.
Replace indoor controller board if it is short-
circuited between - of the drain float
switch connector CN4F and abnormality
reappears.
It is not abnormal if there is no problem about
the above-mentioned ~
Turn the power off, and on again to operate
after check.