Notifier F03 Fault Apr 2026

In this post, we’ll cover exactly what F03 means, its most common causes, and a step-by-step guide to clearing it. On Notifier panels (including the NFS-320, NFS2-640, and ONYX Series), the F03 fault translates to: "Ground Fault."

Few things are more unsettling than a steady yellow LED and an "F03" code staring back at you from your Notifier fire alarm panel. While it’s not a full alarm (fire condition), a fault means your system’s integrity is compromised.

Most Notifier panels will tell you which loop (SLC Loop 1, Loop 2, or NAC circuit) has the ground fault. Write that down.