Mitsubishi Electric City Multi PUMY-P36NHMU Technical & Service Manual page 44

Display Abnormal point and detecting method
5102 Liquid pipe temperature thermistor (TH22)
When the thermistor detects short/open
during the operation, the operation stops
and the operation changes to protect mode
of restarting in 3minutes. If the thermistor
does not recover in 3minutes, the
operation stops due to detecting
abnormality. In this time, <5102> is
displayed. Then, if the thermistor recover
in 3minutes, it operates normally.
Short: Detected 90
Open: Detected -40
Low pressure saturation temperature
thermistor (TH6)
When controller detects short/open in
thermistor during the operation, the outdoor
unit stops once and restarts operation in
3minutes. When the detected temperature
is normal at just before of restarting, the
outdoor unit restarts.
When controller detects short/open in
thermistor at just before of restarting, the
unit stops due to detecting abnormality. In
this time, <5102> is displayed.
For 10 minutes after starting compressor,
heating mode, above-mentioned short/open
are not detected.
Short: 90 [194°F] or more
Open: -40 [-40°F] or less
Connector (CN21 or CN44) contact
failure
Thermistor wiring disconnection or
half disconnection
Thermistor failure
[194°F] or more
[-40°F] or less
Detecting circuit failure in the indoor
controller board
Connector (TH6) contact failure
Thermistor wiring disconnection or
half disconnection
Thermistor failure
Multi controller board input circuit
failure
Causes
44
Check points
Check whether the connector (CN21
or CN44) in the indoor controller
board is connected or not.
Check whether the thermistor wiring
is disconnected or not.
Check the resistance of thermistor;
0 [32°F] ·····15k
10 [50°F] ·····9.6k
20 [68°F] ·····6.3k
30 [86°F] ·····4.3k
40 [104°F] ···3.0k
When there is no problem in above
mentioned , replace the indoor
controller board.
Check whether the connector (TH6)
in the multi controller board is
connected or not.
Check whether the thermistor wiring
is disconnected or not.
Check the resistance of thermistor;
0 [32°F]·····15k
10 [50°F]·····9.6k
20 [68°F]·····6.3k
30 [86°F]·····4.3k
40 [104°F]···3.0k
1 3 4 5 6 7 8 2
on
Set the SW1 to
When the temperature in multi
controller board is not an actual
temperature, replace the multi
controller board.
-42.5: Open
91.9: Short