Lennox Mini-Split Service Manual / Page 150
E3 Flow Chart
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
module and the main board, is it con-
nected 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 nor-
mally.
No
Replace the electric control box.
Problem Solved.
Yes
Yes
No
Yes
Yes
Yes