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