Bosch BMS500-AAU036-1AHCXC - Indoor;Outdoor Communication Error (EL 01)

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Service Manual
Bosch Climate 5000 Series Ductless Air Conditioner / Heat Pump Multi Zone Outdoor Units (01.2023)
8.6.2 Indoor / outdoor communication error (EL O1)
Error Code EL 01
Malfunction decision conditions
Indoor unit does not receive the feedback from outdoor unit for 120 seconds or outdoor unit does not
receive the feedback from any one indoor unit for 180 seconds.
Supposed causes
f Incorrect installation of indoor to outdoor control wire
f Indoor or outdoor PCB faulty
Table 32
Troubleshooting:
Figure 48
Communication malfunction between indoor and
outdoor units
Start: Power off , then Power on the
A/C by the Breaker. (reconnect the
power wire). Is it still displaying the
error code?
Yes
No
Change outdoor unit PCB assembly(include
wiring) totally
Check wiring on the outdoor and indoor
terminal follow the wiring diagram. Is all
connecting correctly?
Yes
No
Measure Vs, is it moving
alternately between positive value
and negative value? (Vs is the
voltage between S and L2).
Refer to Figure 49
Turn on all indoor unit by remote
controller. Is all indoor unit display
Turn off the all indoor units. Is IPM
power LED or operating LED lamp
On?
Yes
Is all the wiring between
terminal and Indoor PCB
connect ok?
No
Yes
No
Reconnect the wiring
Is indoor units number correct? Check
on the outdoor check point . (2 for dual
zone, 3 for tri zone, 4 for qua zone).
Refer
Yes
No first time
Yes
Yes
Change the Indoor PCB
Power on by remote
controller, I
Is it still
displaying the error code
after 3 minutes?
Trouble is solved
No second time
No
Yes
Reconnect the wiring
No
change IPM
No
Is the reactor connecting
well˛
No Reconnect the wiring
Change Outdoor Main PCB
Yes
No
Is main boardĀ ā
lamp on? Refer to
Refer to Figure 50
and Figure 51.
Figure 52.
Figure 53.