What an earth fault, an open or short circuit fault, or a charger fault actually means — and what to do when you see one.
A fault light doesn’t usually mean the building has lost fire alarm protection — but it does mean something on the system isn’t working as it should, and it needs a competent engineer to find and fix it. Never silence or ignore a fault indefinitely — log it, and get it looked at.
What it means: part of the system’s wiring, or a device on it, has an unintended path to earth. On its own, an earth fault usually won’t stop the alarm sounding — but it can mask a second fault developing elsewhere on the same circuit, which is why panels flag it separately.
Common causes: damaged cable insulation, water ingress at a detector or call point, a chafed cable at a containment clip, or a fault inside a device itself.
What to do: note it in the site logbook with the date and time, and call a competent engineer to trace and clear it. Tracing an earth fault means testing sections of the circuit in turn — not something to attempt without the right test equipment and training.
What it means: an open circuit is a break somewhere in the wiring or a disconnected device on that zone or loop — the panel can’t complete its circuit. A short circuit is the opposite: damaged insulation or a device fault is letting two conductors touch that shouldn’t.
Common causes: a loose terminal, a detector removed from its base and not replaced properly, cable damage during other building work, or a failed isolator module on an addressable loop.
What to do: on an addressable loop, short isolators should contain the fault to a small section of devices, so the rest of the loop keeps working — but the fault itself still needs finding and fixing. On a conventional zone, the whole zone can be affected. Either way, this is a wiring-level fault for a qualified engineer, not a DIY fix.
What it means: the panel’s standby battery charging circuit isn’t working as expected — the backup batteries may not be charging correctly, or the charger itself may have failed.
Why it matters: the standby batteries are what keep the fire alarm running during a mains power failure. A charger fault left unresolved risks the system losing backup power exactly when it might be needed most — treat this as a priority call-out, not a “next visit” item.
Common causes: batteries reaching the end of their service life (typically around four years), a failed charging circuit board, or a blown fuse feeding the charger. This applies across Gent, Notifier, Advanced and Morley panels alike.
Call us directly, or request a callback and we’ll talk you through it.
Want to keep a record between visits? Our free Weekly Fire Alarm Testing Logbook covers exactly this, or see our BS 5839 servicing guide for how often a professional visit is needed.
An earth fault means part of the wiring or a device on the system has an unintended path to earth. It won’t usually stop the alarm from working, but it can mask other faults and should be investigated by a competent engineer rather than left on the fault log.
An open circuit is usually a break in the wiring, a loose connection, or a disconnected device on that zone or loop. A short circuit is usually damaged cable insulation or a device fault causing two conductors to touch. Both need an engineer to trace and correct.
A charger fault means the panel’s standby battery charging circuit isn’t working as expected — the batteries may not be charging, or the charger itself may have failed. Left unresolved, the system could lose its backup power during a mains failure, so this should be treated as a priority call-out.
Most panels let you silence the fault buzzer, but that doesn’t fix the underlying problem — it just stops the noise. Finding and correcting the actual fault means testing wiring and devices with the right equipment, which is an engineer’s job.
No. A fault means the panel has detected a problem with the system itself (wiring, power, a device). A false alarm means the fire alarm has activated without an actual fire. Both need investigating, but they show differently on the panel and usually have different causes.