Mitsubishi Electric Mr. SLIM SLZ-M15FA2.TH Technical & Service Manual page 19

9-3. SELF-DIAGNOSIS ACTION TABLE
Check code Abnormal point and detection method
Room temperature thermistor (TH1)
1The 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
minutes. (The unit returns to normal
operation, if it has been reset normally.)
2 Constantly detected during cooling,
drying and heating operation
Short: −90˚C or more
Open: −40˚C or less
P1
Pipe temperature thermistor/Liquid (TH2)
1 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
minutes. (The unit returns to normal
operation, if it has been reset normally.)
2 Constantly detected during cooling,
P2
drying, and heating (except defrosting)
operation.
Short: 90˚C or more
Open: -40˚C or less
Contact failure of drain float switch (CN4F)
• Extract when the connector of drain float
switch is disconnected.
P4
(3 and 4 of connector CN4F is not
short-circuited.)
• Constantly detected during operation
Malfunction of drain pump (DP)
1 Suspensive abnormality, if thermistor of
drain sensor heats itself and temperature
rises slightly. Turn off compressor and
indoor fan.
2 Drain pump is abnormal if the condition
above is detected during suspensive
abnormality.
Constantly detected during drain pump
operation
P5
Drain pump lock protection operation
1 Suspensive abnormality, if drain pump
stops for 5 seconds continuously with
drain pump on.
Drain pump will be restarted after turn-
ing off for 10 seconds.
2 Drain pump is abnormal if the condition
above is detected 4 times during sus-
pensive abnormality.
TCH067A
Note: Errors to be detected in outdoor unit, such as codes starting
with F, U or E (excluding E0 to E7), are not covered in this
document. Please refer to the outdoor unit's service manual
for the details.
Cause
1 Defective thermistor
characteristics
2 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
1 Defective thermistor
characteristics
2 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 temperature
of 90˚C or more or -40˚C or
less.
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
Jamming of the drain float
switch or malfunction of moving
parts causing the drain float
switch to be detected under
water (Switch On)
Defective indoor controller board
1 Malfunction of drain pump
2 Clogged drain pump
3 Disconnected drain pump
Defective indoor controller board
19
Countermeasure
Check resistance value of thermistor.
1–
0˚C ..... 15.0 kΩ
10˚C ....... 9.6 kΩ
20˚C ....... 6.3 kΩ
30˚C ....... 4.3 kΩ
40˚C ....... 3.0 kΩ
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 "9-5.
TEST POINT DIAGRAM". Turn the power
back on 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 checking.
– 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 "9-5.TEST
POINT DIAGRAM". 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
extreme difference with actual pipe <liquid>
temperature, replace indoor controller board.
Turn the power off, and on again to operate
after checking.
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 pump 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.
12 Check if drain pump works.
3 Check if connector (CNP) is connected.
Turn the emergency operation switch (SWE)
on and check the voltage between CNP 1–3.
• Replace drain pump if the output is 13V DC.
• Replace indoor controller board if the output
is under 13V DC.