Mitsubishi Electric CITY MULTI PUMY-P112VKM6 Service Manual page 67

6603 (A3): Transmission bus BUSY error
Abnormal points and detection methods
• Transmission fails due to collision and it continues for 8
to 10 minutes.
• Data cannot be output on the transmission line because
of noise etc. consecutively for 8 to 10 minutes.
Diagnosis of failure
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?
OCH790 _67
Yes
(miswired)
No
(Wired correctly)
Yes
(miswired)
No
(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/dis-
connect transmission from/to control system and cen-
tralized control system.
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).