Mitsubishi Electric CITY MULTI PFFY Series Technical & Service Manual page 15

<Output pulse signal and the valve operation>
Output
(Phase)
1
ON OFF
ø1
ø2 ON ON
OFF ON
ø3
OFF OFF
ø4
➁
Linear expansion valve operation
Close
A
E
B
Extra tightning (80~100pulse)
➂
Trouble shooting
Symptom
Operation circuit fail-
ure of the micro
processor.
Linear expansion
valve mechanism is
locked.
Short or breakage of
the motor coil of the
linear expansion
valve.
Valve doesn
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.
Pulse signal will be sent out for 10 seconds as soon as the
main switch is turn 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) using a tester. It is
normal if the resistance is in the range of
´ To check the linear expansion valve, operate the indoor unit in
t close
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 the
(TH21)
thermistor will go lower. If the detected
Linear
expansion temperature is much lower than the temper-
valve
ature 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.
: 1 → 2 → 3 → 4 → 1
Closing a valve
Opening a valve : 4 → 3 → 2 → 1 → 4
The output pulse shifts in above order.
✻
1. When linear expansion valve operation stops, all output phase
become OFF.
2. At phase interruption or when phase does not shift in order,
motor does not rotate smoothly and motor will locks and vibrates.
✻
When the switch is turned on, 2200 pulse closing valve signal
will be send till it goes to A point in order to define the valve
position.
When the valve move smoothly, there is no noise 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 noise can be heard than normal situation.
✻
Noise can be detected by placing the ear against the screw dri-
ver handle while putting the screw driver to the linear expansion
valve.
Check points
6
5
4
3
2
1
1kΩ LED
200Ω 10%.
Countermeasures
Exchange the indoor con-
troller board at drive circuit
failure.
Exchange the linear
expansion vale.
Exchange the linear
expansion valve.
If large amount of refriger-
ation is leaked, exchange
the linear expansion valve.
Disconnect the connector
at the controller board,
then check the continuity.
14