Service manual

ESIE03–01 Error Codes: System Malfunctions
Part 3 – Troubleshooting 3–65
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4.4 Transmission Error between Indoor and Outdoor Unit (U4 or UF)
Error code U4or UF
Error generation The error is generated when the microprocessor detects that the transmission between the indoor and
the outdoor unit is not normal over a certain amount of time.
Causes The possible causes are:
P Wiring indoor-outdoor transmission wire is incorrect
P Malfunctioning indoor unit PCB
P Malfunctioning outdoor unit PCB
P Outside cause (noise...).
Troubleshooting 1 Diagnosis of incorrect or broken/disconnected wiring. If the LEDs on the indoor unit PC board are off,
it indicates that the transmission wiring between indoor and outdoor units may be incorrect or
broken/disconnected.:
Caution Be sure to turn off power switch before connecting or disconnecting the connector, or parts damage
may occur.
Does
outdoor unit
microcomputer
normal H1P
flash?
Is
indoor-outdoor
transmission wire
connected
correctly?
Is H1P flashing?
NO YES
NO
NO
NO
NO (ON or OFF)
NO (OFF)
YES
YES
YES
Is HAP flashing?
Is HBP flashing?
To outdoor unit
(next page)
Is H2P on?
Check of
indoor unit
microcom-
puter
normal
HAP
Check of
indoor unit
transmission
malfunction
HBP
YES
YES
Turn the power supply off
once and then back on.
Failure of indoor unit PCB or
malfunction of power supply
system.
Resets normally.
Could be outside
cause (noise...).
Failure of indoor unit PCB.
Wire correctly.