Mitsubishi Ecodan fault E5

What it means

Displayed if the FTC cannot find an empty transmission path for 3 minutes and thus cannot transmit, or the data sent by the FTC is different to what was expected 30 consecutive times.

Likely causes

1. 2 or more main remote controllers have been connected to the FTC
2. Fault with main remote controller transmission/receiving circuit board
3. Electrical noise causes interference with transmission/reception of data for main remote controller

Where to start

1. Only connect 1 main remote controller to 1 FTC indoor unit board
2. After installation of outdoor unit, pipework and electrical wiring, recheck that there is no water leakage, loosened connections or miswiring
3. Measure impedance between the ground and the power supply terminal block (L,N) on the outdoor and indoor units with a suitable 500V ohmmeter