LG Multi V Water IV ARNU07GTU 2 Series Service Manual page 68

Troubleshooting Guide
Error
Error Type
No.
Indoor & Outdoor unit
communication error
05
■ Error diagnosis and countermeasure flow chart
Does all the IDUs show
same error code CH05?
Yes
Is outdoor PCB LED
blinking?
Yes
Check if the
communication cable is
properly connected
to indoor / outdoor
terminal block?*
Yes
* (Note1) communication from IDU is normal if voltage
fluctuation(-9V ~ +9V) exists when checking DC voltage
of communication terminal between IDU and ODU
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Error Point
No signal communication
between indoor & outdoor
units.
No
Is total number of indoor
units connected displayed
after auto addressing?
END
No Check the main power
supply at the ODU
terminal block?
Yes
Is main circuit breaker off?
Yes
Improper connection of power supply cable
Main power supply problem
No
Re connect communication cable
Outdoor PCB fault
Replace after checking
Indoor PCB fault
Replace after checking
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Main Reasons
1. Auto addressing is not done
2. Communication cable is not connected
3. Short circuit of communication cable
4. Indoor unit communication circuit fault
5. Outdoor unit communication circuit fault
6. Not enough distance between power and com-
munication cable?
7. T phase line disconnection or N phase connected.
Replace the PCB of indoor unit
No displayed error
Re-connect after check the
communication cable of indoor
unit displayed error**
Replace outdoor PCB after
No
checking
Replace TRANS after checking
Check the insulation of compressor
No
compressor and replace if required
Check the capacity of main circuit
breaker and replace if required
Check T phase line connetion
If all ok,
Turn on main circuit breaker
* If the DC voltage between communication terminal A, B
of indoor unit is fluctuate within (-9V~+9V) then
communication from outdoor unit is normal
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