Mitsubishi Ecodan fault E4

What it means

Displayed if indoor unit does not receive any data from the main remote controller for 3 minutes or indoor unit does not receive any signal from the main remote controller for 2 minutes.

Likely causes

1. Wiring procedure not observed (cable length/cable diameter/number of indoor units/number of main remote controllers)
2. Fault with the main remote controller circuit board
3. Electrical noise causes interference with transmission/reception of data for main remote controller

Where to start

1. Check connection cable for damage or loose connections at the FTC and main remote controller terminals
2. Check main remote controller and FTC common wiring max cable length 500 m, only use 2 core cable, only connect 1 main remote controller to 1 FTC indoor unit board