Liquid Pipe - Mitsubishi Electric City Multi PLFY-P08NCMU-E Technical & Service Manual

<Output pulse signal and the valve operation>
Output
(Phase)
1
ON OFF
{1
ON ON
{2
OFF ON
{3
OFF OFF
{4
2
Linear expansion valve operation
Close
A
E
B
Extra tightening (80~100pulse)
3
Troubleshooting
Symptom
Operation circuit
failure of the micro
processor
Linear expansion
valve mechanism is
locked.
Short or breakage
of the motor coil of
the linear expansion
valve
Valve does not close
completely (thermis-
tor leaking).
Wrong connection
of the connector or
contact failure
Output
2 3 4
OFF ON
OFF OFF
ON OFF
ON ON
C
D
Open
2000 pulse
Opening a valve
all the way
Pulse number
Disconnect the connector on the controller board, then con-
nect LED for checking.
1k
Pulse signal will be sent out for 10 seconds as soon as the
main switch is turned on. If there is LED with lights on or
lights off, it means the operation circuit is abnormal.
Motor will idle and make ticking noise when motor is operated
while the linear expansion valve is locked. This ticking sound
is the sign of the abnormality.
Measure the resistance between the each coil (red-white,
red-orange, brown-yellow, brown-blue) with a tester. It is nor-
mal if the resistance is in the range of 200 i 10%
To check the linear expansion valve, operate the indoor unit
in fan mode and at the same time operate other indoor units
in cooling mode, then check the pipe temperature <liquid pipe
temperature> of the indoor unit by the out-
door multi controller board operation moni-
tor. During fan operation, linear expansion
valve is closed completely and if there are
Thermistor
some leaking, detecting temperature of

(Liquid pipe)

the thermistor will go lower. If the detected
Linear
expansion temperature is much lower than the tem-
valve
perature indicated in the remote controller,
it means the valve is not closed all the
way. It is not necessary to exchange the linear expansion
valve, if the leakage is small and not making any trouble.
Check the color of lead wire and missing terminal of the con-
nector.
Closing a valve : 1 → 2 → 3 → 4 → 1
Opening a valve : 4 → 3 → 2 → 1 → 4
The output pulse shifts in above order.
• When linear expansion valve operation stops, all output phases
become OFF.
• At phase interruption or when phase does not shift in order, motor
does not rotate smoothly and motor will lock and vibrate.
• When the switch is turned on, 2200 pulse closing valve signal will be
sent till it goes to A point in order to define the valve position.
• When the valve moves smoothly, there is no sound or vibration
occurring from the linear expansion valve; however, when the pulse
number moves from E to A or when the valve is locked, more
sound can be heard than normal situation.
• Sound can be detected by placing the ear against the screw driver
handle while putting the screw driver to the linear expansion valve.
Check points
6
5
4
3
2
1
LED
24
Countermeasures
Exchange the indoor con-
troller board at drive circuit
failure.
Exchange the linear expan-
sion valve.
Exchange the linear expan-
sion valve.
If a large amount of refrig-
erant is leaked, exchange
the linear expansion valve.
Disconnect the connector
at the controller board,
then check the continuity.