Mitsubishi Electric MXZ-SM36NAM2 Technical & Service Manual page 64

Check code
Superheat due to low discharge temperature trouble
1500
(U7)
Abnormal points and detection methods
If the discharge superheat is continuously detected −27°F [−15 ](*) or less
for 5 minutes even though the indoor LEV has minimum open pulse after
the compressor starts operating for 10 minutes.
LEV : Linear expansion valve
TH4 : Thermistor <Compressor>
63HS : High pressure sensor
*At this temperature, conditions for the abnormality detection will not be
satisfied if no abnormality is detected on either TH4 or 63HS.
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Is the TH4 wiring disconnected?
Check the resistance of TH4.
Is the resistance normal?
Check the connector contact and wiring of
the indoor LEV.
Is there any abnormality
such as half-disconnection or
breakage?
Disconnect the indoor LEV wiring to check
the resistance.
Continue to the next page.
OCH810A
Diagnosis
(disconnected)
(connected properly)
No
Yes
..
No
Causes and checkpoints
Disconnection or loose connection of TH4
Defective holder of TH4
Disconnection of LEV coil
Disconnection of LEV connector
LEV performance failure
Connect the wiring properly.
Yes
32°F [0°C]·······700kΩ 50°F [10°C]·····410kΩ
68°F [20°C]·····250kΩ 86°F [30°C]·····160kΩ
104°F [40°C]·····104kΩ
No
Connect the connector properly, or replace
Yes
the LEV.
64
Chart 1 of 2
Remedy
Replace the TH4.