Check code
Abnormal points and detection methods
Causes and checkpoints
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.
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.
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Diagnosis
Remedy
6603
(A3)
Transmission bus BUSY error
No
Yes
Yes
Yes
No
No
78
OCH675E
Is the transmission line miswired?
Is the transmission line miswired?
Does it operate normally?
Correct the wiring, then turn the power
back ON.
Correct the wiring, then turn the power
back ON.
Replace the indoor/outdoor controller
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).
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.
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.
Turn the power back ON.
(miswired)
(miswired)
(wired correctly)
(wired correctly)