00

Communication Error (Indoor/Outdoor/Remote Controller)

Mitsubishi Electric · PAR-21MAA MA Remote Controller

What does 00 mean?

A communication error exists within the system, potentially due to an open or shorted remote controller transmission wire (S1, S2, S3), or an outdoor unit configured with an address other than 0. The outdoor board LED shows only green after startup, and the remote controller may have no display or its display may quickly disappear.

Repair Steps

  1. 1

    Verify the continuity and integrity of the remote controller transmission wire (S1, S2, S3) between the indoor and outdoor unit using a multimeter, checking for both open circuits and short circuits.

  2. 2

    Check the outdoor unit's address setting; ensure the indoor unit is configured to connect to an outdoor unit with address '0'.

  3. 3

    Verify that all remote controller transmission wire connections at the terminal blocks (S1, S2, S3) are secure and correctly wired with proper polarity.

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Verified technical data. Last updated: March 2026
Source: Mitsubishi Electric PAR-21MAA MA Remote Controller