Mitsubishi Electric EE

What does Mitsubishi Electric EE mean?

EE indicates a communication error between the indoor and outdoor units. The two units must continuously exchange data over the connecting wiring to coordinate operation; when that exchange fails, EE is shown and the system stops normal operation. As with other communication faults, the cause is typically in the connecting wiring, terminal connections, or a control board, not the refrigerant circuit.

Symptoms

• EE displayed on the controller
• Indoor and outdoor units not coordinating
• No cooling or heating output
• Fault appears after wiring work or power events

Common causes

• Loose or disconnected connecting wiring
• Miswired or reversed S1/S2/S3 connections
• Power problem at the outdoor unit
• Indoor or outdoor control board fault

Diagnostic steps

1. 01

   Power down both units

   Switch off the indoor and outdoor units before inspecting wiring.

2. 02

   Inspect the connecting wiring

   Check that the connecting wires between the units are secure and correctly matched.

3. 03

   Confirm outdoor power

   Verify the outdoor unit has power at its terminal block.

4. 04

   Reseat terminals

   Reseat the terminal connections to restore communication.

5. 05

   Restart and confirm

   Restore power and check whether EE clears.

When to call a professional

Call a technician if EE persists after the connecting wiring is checked, since verifying the line and isolating whether an indoor or outdoor board is at fault requires service data and meters. The connecting wiring and any board replacement involve mains-voltage work and should be carried out by a qualified HVAC professional.