Mitsubishi Electric PKFY-20VAM Technical & Service Manual page 11

<Output pulse signal and the valve operation>
Output
(Phase)
1
ON OFF
{1
ON ON
{2
OFF ON
{3
OFF OFF
{4
Linear expansion valve operation
Close
A
E
B
Extra tightning (80~100pulse)
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't 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 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 150'+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
outdoor multi controller board operation
monitor. During fan operation, linear
expansion valve is closed completely and if
Thermistor
there are some leaking, detecting tempera-
ture of the thermistor will go lower. If the
Linear
detected temperature is much lower than
expansion
valve
the temperature 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
Opening a valve : 4 3
The output pulse shift in above order.
1. When linear expasion 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 lock, and vibrates.
When the switch is turned on, 2200 pulse opening valve signal
will be send till it goes to
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
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
LED
3 4 1
2 1 4
point in order to define the valve
A
to or when the valve is locked,
E A
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 thermis-
tor is leaked, exchange the
linear expansion valve.
Disconnect the connector
at the controller board,
then check the continuity.
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