Troubleshooting Of Each Part - Mitsubishi Electric PRH-P8MYA Technical & Service Manual

[7] Troubleshooting of each part

(1) LEV
1) Overview of LEV operation
LEV (electronic expansion valve) receives pulse signals from the outdoor-side controller board and drives a valve
by means of a servomotor.
The valve opening angle changes in proportion to the number of pulses.
<Outdoor-side controller board and LEV>
Brown
Yellow
White Red Orange
Output (phase)
No.
1
ø1
ON
ø2
ON
ø3
OFF
ø4 OFF
LEV opening and closing operations
Valve closing
A
E
B
Increased throttling region (80 - 100 pulses)
Blue
Output state
2 3 4
OFF OFF ON
ON OFF OFF
ON ON OFF
OFF ON ON
D
C
Valve opening
Full open
2000 pulses
Pulse count
Brown
Red
Blue
Yellow
White
Connector
Outdoor-side controller board CN40
<Pulse signal output and valve operation>
The output pulses change in the following order:
1 → 2 → 3 → 4 → 1
Valve closing
4 → 3 → 2 → 1 → 4
Valve opening
*1. When the LEV opening angle is not changed, all output
phases turn OFF.
2. When the output misses a phase or remains ON, the mo-
tor cannot rotate smoothly and makes a clacking sound
and vibrates.
* When the power is turned on, to register the valve posi-
tion, a 2200 pulses valve close signal is output and is al-
ways set to point A .
If the valve moves smoothly, the LEV will not generate a sound
or vibration, but at E → A and when the valve is locked, a
sound louder than the sound generated by missing phase,
etc. will be generated.
* Generation of sound can be checked by placing the tip of
a screwdriver against the valve and your ear against the
handle.
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Drive circuit