Mitsubishi Electric PLFY-P32VBM-E Service Manual page 21

<Output pulse signal and the valve operation>
Output
(Phase)
1
{1 ON OFF
ON ON
{2
OFF ON
{3
OFF OFF
{4
Linear expansion valve operation
Open
Close
A
E
Close
B
Extra tightening (200~800 pulse)
Troubleshooting
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.
Wrong connection of
the connector or
contact failure
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 sec-
onds. 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
ticking sound is the sign of the abnormality.
Measure the resistance between each coil (white-red, yellow-
brown, orange-red, blue-brown) with a tester. It is normal if
the resistance is in the range of 150Ω ±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 is any leaking, detecting temperature
(Liquid pipe)
of the thermistor will go lower. If the detect-
Linear
ed temperature is much lower than the tem-
expansion
valve
perature indicated in the remote controller,
it means the valve is not closed all the way. It is not neces-
sary 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
Opening a valve : 4 3
The output pulse shifts in above order.
• When linear expansion valve operation stops, all output phase
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 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
sound 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
21
3 4 1
2 1 4
in order to define the valve position.
to or when the valve is locked, more
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 refriger-
ant is leaked, exchange
the linear expansion valve.
Disconnect the connector
at the controller board,
then check the continuity.