Carrier 42QHF009DS Service Manual page 66

E3 display
Communication malfunction between
IPM board and outdoor main board
Is there at least one LED in
the IPM board light?
No
Check the signal wire between
the IPM board and the main
board, is it connected good?
No
Reconnect and retry. Is
error still display?
No
Replace IPM board, and
then check whether the
system can run normally
No
Replace outdoor main
board, and then check
whether the system can run
normally
No
Replace the electric control
box
12.3.2.3 Voltage protection(ODU E5)
Yes
Yes
No
Yes
Yes
Trouble is solved
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