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26-26

Code 26-26 PCM MCU Old Version A - Microcontroller on board is an old version.

Carrier · Air Conditioners & Heat Pumps

What does 26-26 mean?

This fault indicates that the microcontroller on the installed PCM (Processor Control Module) board is an older version than required. Boards with this fault should not be used in operation.

Common Causes

  • Outdated PCM microcontroller software or hardware.
  • Incorrect PCM board installed.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Identify the PCM board installed in your Carrier unit.

  2. 2

    This board is considered old and should not be used in the field.

  3. 3

    Contact Carrier support or your installer for a warranty replacement of the PCM board.

  4. 4

    Ensure the replacement PCM board has the most current software version.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

14-94Code 14-94 Line Voltage Low — Incoming voltage is too low15-94Code 15-94 Line Voltage High — Incoming voltage is too high17-06Code 17-06 Lost BTM Communication — Bluetooth module not communicating with control board
Source: Carrier Air Conditioners & Heat Pumps
Open Manual (Page 16)Search more codes in this manual