Mitsubishi Electric PRH-P8MYA Technical & Service Manual page 70

<Abnormality detected during unit operation: Indoor-side unit>
Abnormal- Meaning of abnormality display and
ity display abnormality troubleshooting
Remote control communication re-
ceive abnormal
1) When the indoor-side controller
board can not receive data
normally from the remote
controller or another indoor-side
controller board even once in
E4 3 minutes, an abnormality is
recognized.
2) When the indoor-side controller
board can not receive signals
even once in 2 minutes, an
abnormality is recognized.
Cause
(1) Remote controller transmission line
contact faulty.
(2) All remote controllers set as "slave"
remote controller.
(3) Remote controller send/receive circuit
faulty.
(4) Indoor-side controller board send/
receive circuit faulty.
(5) Noise entered on remote controller
transmission line.
- 67 -
Judgment method and remedy
(1) Check if the unit or remote controller
transmission line disconnected or
loose.
(2) Set one remote controller as "master".
When there are no problems at the
above
(3) Perform remote controller diagnosis.
a) [RC OK] display
Remote controller normal.
Check by turning power off and on.
If the abnormality occurs again, replace
indoor-side controller board.
b) [RC NG] display
Replace remote controller.
c) [RC E3] display
[ERC00-66] noise, etc. is probable
cause.