Error 203 — Communication error between main and sub outdoor units

What does 203 mean?

This error indicates a communication problem between the primary outdoor unit and any secondary (sub) outdoor units in a multi-unit system. This prevents coordinated operation.

• Faulty communication cable between outdoor units
• Incorrect address configuration for sub outdoor units
• Power supply issue to a sub outdoor unit
• Control board malfunction in one of the outdoor units

Click steps to track your progress.

1. 1

   Switch off the power to all outdoor units in the system from the main electrical panel.

2. 2

   Examine the communication cable that links the main outdoor unit to the sub outdoor units for damage or loose connections.

3. 3

   Confirm that the address settings for each sub outdoor unit are correct and unique according to the installation manual.

4. 4

   Ensure that all outdoor units are receiving proper power.

5. 5

   Restore power to all units and check for system communication. If the error persists, an HVAC technician should perform further diagnostics.