Transmission Bus Busy Error; 6603 - Mitsubishi Electric PUMY-P250YBM Technical & Service Manual

Check code

6603

(A3)
Abnormal points and detection methods
An abnormality when no transmission status caused by transmitting
data collision continues for 8 to 10 minutes.
An abnormality when data cannot be output on the transmission line
consecutively because of noise etc. for 8 to 10 minutes.
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Check whether the transmission line to the indoor unit,
Fresh Master, Lossnay or remote controller is miswired
to the terminal block (TB7) on outdoor unit or not.
Is the transmission line miswired?
Check whether the transmission line with the other refrigerant
system of the indoor unit, Fresh Master or Lossnay is miswired
to the terminal block (TB3) on outdoor unit or not.
Is the transmission line miswired?
Turn the power back ON.
Does it operate normally?
OCH760

Transmission bus BUSY error

Diagnosis
(miswired)
(Wired correctly)
No
(miswired)
(Wired correctly)
No
Yes
Causes and checkpoints
The transmission processor is unable to transmit due
to a short-cycle voltage such as noise is mixed on
the transmission line.
The transmission processor is unable to transmit due
to an increase of transmission data amount caused
by a miswiring of the terminal block (transmission
line) (TB3) and the terminal block (centralized control
line) (TB7) on the outdoor unit.
The share on transmission line becomes high due
to a mixed transmission caused by a malfunction
of repeater on the outdoor unit, which is a function
to connect/disconnect transmission from/to control
system and centralized control system.
Correct the wiring, then turn the power
Yes
back ON.
Correct the wiring, then turn the power
Yes
back ON.
Replace the indoor/outdoor controller
No
board.
There is no abnormality on the AC unit.
It might be caused by an external noise, so check
the transmission line to remove the factor(s).
76
Remedy