Title: Before Replacing the Furnace Control Board: Troubleshooting Error Codes
Issued by: Daikin Comfort Technologies North America
Date: March 30, 2026

Purpose

This Technical Service Bulletin (TSB) instructs service technicians to fully troubleshoot furnace error codes before replacing the control board. Revision 1 introduces expanded troubleshooting tables in furnace service manuals with more detailed possible causes and corrective actions.

Key Points

General Guidance

• Many error codes are not caused by a failed control board.
• Improper wiring, grounding, or connected components are more common root causes.
• Always review stored fault history (F10 – Last 10 Faults) before replacing parts.

Overall Message

Do not replace the furnace control board until wiring, grounding, components, and error history have been thoroughly checked. Most reported issues are external to the control board itself.

See attached file for the full bulletin with troubleshooting steps for common error codes.