Mitsubishi Electric PLFY-P05NFMU-E Technical & Service Manual page 22

<Output pulse signal and the valve operation>
Output
(Phase)
1 2
{1
ON OFF
{2
ON ON
{3 OFF ON
{4
OFF OFF
2 Linear expansion valve operation
Open
Close
A
E
Close
B
Extra tightening (200~800pulse)
3 Troubleshooting
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
OCH604A
Output
Closing a valve : 1
3 4
Opening a valve : 4
OFF ON
The output pulse shifts in above order.
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
Symptom
Disconnect the connector on the controller board, then con-
nect LED for checking.
When power is turned on, pulse signals will be 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 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 200
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
Thermistor
(Liquid pipe)
Linear
expansion
valve
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.
2 3
3 2
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 power is applied valve drives in the closed direction 2200
pulses and will end at This is done to define valve position.
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
E
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
10 .
li 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
is any leaking, detecting temperature of
the thermistor will go lower. If the detected
temperature is much lower than the tem-
perature indicated in the remote controller,
it means the valve is not closed all the way.
22
4 1
1 4
to or when the valve is locked, more
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 large amount of refriger-
ant leaks, exchange the
linear expansion valve.
Disconnect the connector
at the controller board,
then check the continuity.