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Red LED Keeps Flashing, Green LED Stays OFF (Option Control)

Red LED Keeps Flashing, Green LED Off - Communication error (option control in-use)

Mitsubishi Heavy Industries · Air Conditioners

What does Red LED Keeps Flashing, Green LED Stays OFF (Option Control) mean?

The indoor unit's red LED keeps flashing and the green LED stays off. This indicates a communication error within an optional control unit, such as SC-SL2NA-E or SC-SL4-AE/BE.

Common Causes

  • Defective communication circuit on the main unit of the optional controller

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Turn off the air conditioner at the main power breaker, wait for 5 minutes, and then turn it back on.

  2. 2

    Ensure all connections to the optional control unit are secure and undamaged.

  3. 3

    If the error persists, contact a qualified technician to diagnose and potentially replace the optional control unit's PCB.

Browse all codes in this manual (110)
Verified technical data. Last updated: April 2026

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Source: Mitsubishi Heavy Industries Air Conditioners
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