Possible Problems And Solutions - Mitsubishi Electric PUHY-HP72 Service Handbook

[8-8 Troubleshooting LEV Problems ]
8-8-2

Possible Problems and Solutions

The specifications of the outdoor unit (outdoor LEV) and the indoor unit (indoor LEV) differ. Therefore, remedies for each fail-
ure may vary. Check the remedy specified for the appropriate LEV as indicated in the below column.
Malfunction
mode
Microcomputer Disconnect the control board connector and connect the check
driver circuit fail- LED as shown in the figure below.
ure
Resistance : 0.25W 1k
LED : DC15V 20mA or more
When the main power is turned on, the indoor unit circuit board
outputs pulse signals to the indoor unit LEV for 10 seconds, and
the outdoor unit circuit board outputs pulse signals to the outdoor
unit LEV for 17 seconds.
If any of the LED remains lit or unlit, the drive circuit is faulty.
LEV mechanism If the LEV is locked, the drive motor runs idle, and makes a small
is locked clicking sound.
When the valve makes a closing and opening sound, the valve
has a problem.
Disconnected or Measure the resistance between coils (red-white, red-orange,
short-circuited brown-yellow, brown-blue) with a tester. When the resistance is
LEV motor coil in the range of 150 ± 10%, the LEV is normal.
Measure the resistance between coils (red-white, red-orange,
red-yellow, red-blue) with a tester. When the resistance is in the
range of 100 ± 10%, the LEV is normal.
Measure the resistance between coils (red - white, red - orange,
brown - yellow, brown - blue) with a tester. When the resistance
is in the range of 46 ± 3%, the LEV is normal.
Incomple sealing When checking the refrigerant leak from the indoor LEV, run the
(leak from the target indoor unit in the fan mode, and the other indoor units in
valve) the cooling mode. Then, check the liquid temperature (TH2) with
the self-diagnosis LED. When the unit is running in the fan mode,
the LEV is fully closed, and the temperature detected by the
thermistor is not low. If there is a leak, however, the temperature
will be low. If the temperature is extremely low compared with the
inlet temperature displayed on the remote controller, the LEV is
not properly sealed, however, if there is a little leak, it is not nec-
essary to replace the LEV when there are no effects to other
parts.
Faulty wire con- 1. Check for loose pins on the connector and check the col-
nections in the ors of the lead wires visually
connector or
2. Disconnect the control board's connector and conduct a
faulty contact
continuity check using a tester.
28
- chapter 8
Judgment method
6
5
4
3
2
1
1 k LED
Thermistor
(liquid piping
temperature detection)
Linear Expansion Valve
Remedy
When the drive circuit has a
problem, replace the control
board.
Replace the LEV.
Replace the LEV coils.
Replace the LEV coils.
Replace the LEV coils.
If there is a large amount of
leakage, replace the LEV.
Check the continuity at the
points where an error occurs.
Target
LEV
Indoor
Outdoor
Indoor
Outdoor
Indoor
Outdoor
(LEV2a,
LEV2b)
Outdoor
(LEV1,
LEV4,
LEV9)
Indoor
Indoor
Outdoor
HWE18240_GB