Mitsubishi Electric PRH-P8MYA Technical & Service Manual page 71

<Troubleshooting and repair by symptom>
Symptom and operation when normal
1. No remote controller display
2. Remote controller displays "H0" un-
changed.
3. When remote controller operation
switch pressed, operation display
appears but immediately disap-
pears.
4. Does not beep and air conditioner
does not operate even when oper-
ated with wireless remote control-
ler.
(Operation display appears on wire-
less remote controller.)
5. When operated with wireless re-
mote controller, beeps but does not
operate.
6. Remote controller display is normal
and cooling operation is performed,
but without any capacity (does not
cool).
Cause
(1) DC14V is not supplied to remote con-
troller.
(No power O display on liquid crystal
panel.)
(2) DC14V is supplied to remote controller
but nothing is displayed.
- "H0" not displayed
- "H0" displayed
(1) Remote controller displays "H0" for
maximum of 2 minutes for starting after
power turned on.
(2) Indoor-remote controller communication
faulty.
(3) Outdoor-indoor controller boards
communication faulty.
(1) Operation switch is disabled for approxi-
mately 30 seconds after function select
operation from remote controller is re-
leased.
(1) Wireless remote controller and
indoor-side controller board pair
number setting mismatched.
(2) Cause of item 1.
(1) Air conditioner does not operate for a
maximum of 2 minutes after the power
is turned on.
(2) Set to local operation prohibit mode.
- Remote start/stop adapter is con-
nected to CN32 on indoor-side
controller board.
- Air conditioner is connected to
MELANS and is set to local operation
prohibit mode from centralized control-
ler, etc.
(3) Cause of item 2.
(1) Insufficient refrigerant.
(2) Filter clogged.
(3) Outdoor-side heat exchanger clogged.
(4) Air duct short cycle.
(5) LEV malfunction
- 68 -
Symptom judgment and remedy
(1) Check LED2 on indoor-side controller board.
1) Steady light
Check remote controller wire open or faulty
contact.
2) Flashing
Check for remote controller wire short.
3) Not lit
Check outdoor-side controller refrigerant
address.
(2) Make the following judgment:
- When "H0" is not displayed, remote control-
ler is faulty.
- When "H0" is displayed, see item 2.
(1) Normal operation.
(2) Remote controller self-diagnosis.
(3) When outdoor-indoor controller boards cannot
communicate, "H0" is displayed for a
maximum 6 minutes.
Check LED3 on indoor-side controller board.
1) Does not flash
Check indoor/outdoor controller boards
connection cable for erroneous wiring.
(S1 and S2 or S3 open)
2) Flashes
Indoor/outdoor contorller boards connection
cable is normal.
(1) Normal operation.
(1) Check pair number setting.
(2) Item check of item 1.
(1) Normal operation.
(2) Normal operation.
(3) Item check of item 2.
(1) - When there is leakage, discharge tempera-
ture rises. Therefore, check by measuring
temperature.
- Check for gas leakage from piping connec-
tions, etc.
(2) Open intake grille and check filter. Clean filter,
and remove dust and dirt.
(3) - Since both indoor-side piping temperature
and outlet pressure rise when filter clogged,
judge by measuring outlet pressure.
- Clean heat exchanger.
(4) Remove obstruction.
(5) Check refrigerant circuit operation state.