Mitsubishi Electric CITY MULTI PQRY-P200YMF-B Service Handbook page 83

Judgment methods and likely failure mode
Caution:
The specifications of the heat source unit (heat source LEV) and indoor unit (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
1 Disconnect the control board connector and connect
driver circuit
the check LED as shown in the figure below.
failure
Indoor, BC controller
When the base power supply is turned on, the indoor LEV
outputs pulse signals for 10 seconds, the heat source LEV
outputs pulse signals for 17 seconds, and BC controller
outputs pulse signals for 10-20 seconds.
If the LED does not light up, or lights up and remains on,
the driver circuit is abnormal.
LEV mechanism
1 If the LEV is locked up, the drive motor turns with no
is locked.
load 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 150Ω ± 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 46Ω ± 3%.
Fully closed
1 If you are checking the indoor unit's LEV, operate the
failure (valve
indoor unit's blower and the other indoor units in the
leaks)
cooling mode, then check the piping temperatures
(liquid pipe temperatures) of the indoor units by the
operation monitor through the heat source unit's
control board. When the fan is running, the linear
expansion valve is fully closed, so if there is leakage,
minimal leakage, it is not necessary to replace the
LEV if there are no other effects.
Faulty wire
1 Check for pins not fully inserted on the connector and
connections in
check the colors of the lead wires visually.
the connector or
2 Disconnect the control board's connector and conduct
faulty contact.
a continuity check using a tester.
Judgment Method
Heat source
the temperature sensed by the
Thermistor
thermistor (liquid pipe temperature
liquid pipe
sensor) will become low. If the
(tempera-
temperature is considerably low
ture sensor)
compared to the remote control's
Linear
intake temperature display, it can
Expansion
be judged that there is a fully
Valve
closed failure. In the case of
Treatment
In the case of driver circuit
failure, replace the 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.
–80–
Affected LEV
Indoor
BC controller
Heat source
Indoor
BC controller
Heat source
Indoor
BC controller
Heat source
Indoor
BC controller
Indoor
BC controller
Heat source