Mitsubishi Electric City Multi CMB-P1016NU-G, Service Handbook

Page: 285 / 349

- 276 -
[
IX
Troubleshooting ]
(2) Heat source unit LEV
The valve opening changes according to the number of pulses.
<Connections between the heat source unit MAIN board and LEV1, and the heat source unit MAIN board and LEV2 (heat
source unit expansion valve)>
Pulse signal output and valve operation
LEV valve closing and opening operation
LEV
DC 12V
Heat source unit MAIN board
M
4
6
2
3
5
1
4
5
6
3
2
1
4
5
6
3
2
1
4
3
2
1
Red
Brown
Blue
Orange
Yellow
White
Drive circuit
1 2 3 4 5 6 7 8
1 ON OFF OFF OFF OFF OFF ON ON
2 ON ON ON OFF OFF OFF OFF OFF
3 OFF OFF ON ON ON OFF OFF OFF
4 OFF OFF OFF OFF ON ON ON OFF
[Pulse signal output and valve operation]
Output pulses change in the following orders when the
Valve is closed; 1 2 3 4 5 6 7 8 1
Valve is open; 8 7 6 5 4 3 2 1 8
*1. When the LEV opening angle does not change,
all the output phases will be off.
*2. When the output is open phase or remains ON,
the motor cannot run smoothly, and rattles and vibrates.
Output
(phase)
number
Output state
*When the power is turned on, the valve closing signal of 520 pulses
will be output from the indoor board to LEV to fix the valve position.
It must be fixed at point A.
(Pulse signal is output for approximately 17 seconds.)
When the valve operates smoothly, there is no sound from the LEV and no
vibration occurs, but when the valve is locked, noise is generated.
*Whether a sound is generated or not can be determined by
holding a screwdriver against it, then placing your ear against the handle.
*If liquid refrigerant flows inside the LEV, the sound may become smaller.
B
A
Fully open: 480 pulses
Pulses
Valve opening (refrigerant flow rate)
Valve closed
Valve open