Mitsubishi Electric PLFY-P20VEM-E Technical & Service Manual page 24

<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
Open
Close
A
E
Close
B
Extra tightening (200–800 pulse)
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.
Wrong connection
of the connector or
contact failure
OCH657
Output
2 3 4
OFF ON
OFF OFF
ON OFF
ON ON
C
D
Open
Outdoor unit R410A model
Outdoor unit R22/R407C model : 2000 pulse
Opening a valve
all the way
Pulse number
Disconnect the connector on the controller board, then con-
nect LED for checking.
When power is turned on, pulse signals will output for 10
seconds. There must be some defects in the operation circuit
if the LED does not light while the signals are output or keeps
lighting even after the signals stop.
Motor will idle and make a ticking noise when the motor is
operated while the linear expansion valve is locked. This tick-
ing sound is a sign of abnormality.
Measure the resistance between each coil (white-red, yellow-
brown, orange-red, blue-brown) using a tester. It is normal if
the resistance is in the range of 200Ω ±10%.
To check the linear expansion valve, operate the indoor unit
in fan mode and at the same time operate the other indoor
units in cooling mode, then check the pipe temperature <liq-
uid pipe temperature> of the indoor unit by
the outdoor multi controller board operation
monitor. During fan operation, linear expan-
sion valve is closed completely and if there
Thermistor
is any leaking, detecting temperature of
(Liquid pipe)
the thermistor will go lower. If the detected
Linear
temperature is much lower than the tem-
expansion
valve
perature indicated on 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 affecting normal operation.
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.
Note:
· 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 power is turned on, 2200 pulse closing valve signal will be
sent till it goes to point
A
When the valve moves smoothly, there is no sound or vibration
occurring from the linear expansion valves, however, when the pulse
number moves from to
E
can be heard than in a normal situation.
· Sound can be detected by placing the ear against the screw driver
handle while putting the screw driver tip to the linear expansion
valve.
: 1400 pulse
Check points
6
5
4
3
2
1
1k" LED
24 24
in order to define the valve position.
or when the valve is locked, more sound
A
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
on the controller board,
then check for continuity.