Mitsubishi Electric CITY MULTI PUHY-400YMF-B Service Handbook page 138

Judgment Methods and Likely Failure Mode
Caution
The specifications of the outdoor unit (outdoor LEV) and outdoor units (indoor LEV) differ. For this reason, there are cases
where the treatment contents differ, so follow the treatment specified for the appropriate LEV as indicated in the right
column.
Failure Mode
Microcomputer Disconnect the control board connector and connect the
Driver Circuit check LED as shown in the figure below.
Failure
<LEV1, SLEV>
Ω
1k
When the base power supply is turned on, the indoor LEV
outputs pulse signals for 10 seconds.
If the LED does not light up, or lights up and remains on,
the driver circuit is abnormal.
LEV mechanism If the LEV is locked up, the drive motor turns with no load
is locked. and a small clicking sound is generated.
Generation of this sound when the LEV is fully closed or
fully open is abnormal.
The LEV motor Measure the resistance between the coils (red - white, red
coils have a - orange, brown - yellow, brown - blue) using a tester. They
are normal if the resistance is within 150 Ω ± 10 %.
disconnected wire
or is shorted.
Measure the resistance between the coils (gray - orange,
gray - red, gray - yellow, gray - black) using a tester. They
are normal if the resistance is within 46 Ω ± 3 %.
Fully Closed If you are checking the indoor unit's LEV, operate the
Failure (valve indoor unit in fan mode and at the same time operate other
leaks) indoor units in the cooling mode, then check the piping
temperatures (liquid pipe temperatures) of the indoor unit
by the operation monitor through the outdoor unit controller
board. When the fan is running, the linear expansion valve
is fully closed, so if there is leakage, the temperature
sensed by the thermistor (liquid pipe temperature sensor)
Linear
Expansion
Valve
1 Check for pins not fully inserted on the connector and
Faulty wire
connections in the check the colors of the lead wires visually.
connector or faulty 2 Disconnect the control board's connector and conduct
contact. a continuity check using a tester.
Judgment Method
LED
will become low. If the temperature
is considerably low compared to
the remote control's intake
temperature display, it can be
judged that there is a fully closed
Thermistor
failure. In the case of minimal
leakage, it is not necessary to
replace the LEV if there are no
other effects.
In the case of driver circuit
failure, replace the indoor unit's
<LEV2> control board.
Replace the LEV.
Replace the LEV coils.
Replace the LEV coils.
If there is a large amount of
leakage, replace the LEV.
Check the continuity at the
places where trouble is found.
–135–
Treatment Affected LEV
Indoor
Outdoor
Indoor
Outdoor
Indoor
Outdoor
Indoor
Indoor
Outdoor