Daikin VRVII Manual page 291

Troubleshooting
Caution
Has
the indoor
or outdoor unit
PCB been
replaced, or has the
indoor - outdoor or
outdoor - outdoor
unit transmission
wiring been
modified?
NO
All indoor
unit remote
controllers of the same
refrigerant system
display "U4".
YES
Reset the power supply.
Outdoor
unit PCB micro-
computer monitor
(HAP) blinks.
YES
B
286
Troubleshooting by Indication on the Remote Controller
Be sure to turn off the power switch before
connecting or disconnecting connectors, or parts
may be damaged.
YES
NO
Is indoor -
outdoor and
outdoor - outdoor unit
transmission wiring
normal?
NO
voltage between
terminals L1 and N of
the outdoor unit PCB
is 220~240 V.
YES
NO
The
NO
YES
A
Press and hold
the RESET
button on the
outdoor unit main
PCB for 5
seconds.
∗ The unit will not
operate for up
to 12 minutes.
Replace the
indoor unit PCB
indicated by the
error code "U4".
Fix the indoor-
outdoor or
outdoor-outdoor
unit transmission
wiring.
Supply 220~240 V.