Your Eaton UPS is beeping. There’s an alarm on the display. Maybe it’s a fault code you’ve never seen before, maybe it’s a persistent alarm that keeps clearing and returning. This guide covers the most common Eaton UPS fault codes and alarms encountered in Canadian facilities — what they mean, which ones are urgent, and what to do next.
Note: This guide covers Eaton 5P, 9PX, 9SX, 9130, and 9E series UPS systems. Older Powerware models (9315, 9390) use a different fault display system but follow similar diagnostic logic.
The Three Alarm Categories
Before diving into specific codes, it helps to understand how Eaton categorises alarms:
- Informational alerts — the UPS is operating normally but wants you to know something (e.g., a scheduled battery test completed).
- Warning alarms — the UPS is still protecting your load, but a condition exists that requires attention. Don’t ignore these; they often precede a fault.
- Fault conditions — the UPS has transferred to bypass or shut down. Your load may or may not be protected depending on the type of fault. These require immediate action.
Battery Alarms
Replace Battery / Battery Fault
What it means: The UPS ran a self-test and one or more battery cells failed to hold voltage. The battery pack is degraded and cannot provide rated backup time.
Urgency: High. A battery that fails a self-test under light load may fail completely under actual load during a power event. Schedule battery replacement promptly.
What to do: Note the battery age. If batteries are 3+ years old, plan replacement. If they’re newer than 3 years, the fault may indicate premature degradation due to heat, deep discharge cycles, or a bad cell in the pack. A load test will confirm actual remaining runtime.
Low Battery / Imminent Shutdown
What it means: The UPS is on battery (utility power failed or was interrupted) and the battery charge is nearly depleted. The UPS will shut down within minutes.
Urgency: Critical. If utility power hasn’t returned, initiate a graceful shutdown of connected equipment immediately.
Battery Disconnected
What it means: The UPS cannot detect the battery module. This can occur after a HotSwap module replacement if the module isn’t fully seated, or it can indicate a failed battery connector or internal wiring issue.
What to do: If this appeared after a battery replacement, re-seat the module. If it appears spontaneously, the UPS requires on-site inspection.
Bypass and Protection Alarms
On Bypass / In Bypass Mode
What it means: The UPS has transferred your load to utility power directly — bypassing the inverter, charger, and battery. Your equipment is no longer conditioned or protected against power interruptions.
Urgency: High. The UPS transferred to bypass because of an internal fault. The fault must be diagnosed before the UPS can return to normal online operation.
Common causes: Inverter fault, overload, thermal shutdown (overheating), output short circuit, or deliberate bypass mode activated during maintenance.
Overload
What it means: The connected load exceeds the UPS’s rated output capacity.
What to do: Check the load percentage on the front panel. If the UPS is above 80% capacity, identify which devices are drawing the most power and either redistribute the load to another circuit or replace the UPS with a higher-capacity model. A load that regularly runs above 80% reduces battery and inverter lifespan significantly.
Input Power Alarms
Input Voltage Out of Range / Input Undervoltage / Input Overvoltage
What it means: The utility input voltage is outside the UPS’s acceptable input range. For Canadian facilities (120V single-phase), the 9PX typically accepts 80–150V. A persistent out-of-range alarm suggests a building wiring issue or utility supply problem rather than a UPS fault.
What to do: Measure actual input voltage at the UPS. If the input voltage is consistently abnormal, contact your electrical contractor or utility provider. If the UPS is transferring to battery frequently due to input voltage sags, consider expanding the input voltage window in the UPS settings.
On Battery
What it means: Utility power is unavailable and the UPS is running from battery. This is normal during a power outage. If this alarm appears repeatedly for short periods (seconds to minutes) during normal operation, you have a power quality problem — voltage sags, brief interruptions, or frequency deviation — that is causing the UPS to transfer to battery unnecessarily.
Charger and Inverter Faults
Charger Fault
What it means: The battery charger circuit has failed or is not operating correctly. The UPS may still be providing power via the inverter, but the batteries are not charging. If utility power fails, your backup time depends entirely on whatever charge remains in the battery.
Urgency: High. A charger fault on a 9PX, 9SX, or 9130 typically requires a component-level repair or board replacement. This is not a field-serviceable item for most facilities teams.
Inverter Fault
What it means: The inverter — the component that converts DC battery power to AC output — has failed or is reporting an error. The UPS will likely have transferred to bypass.
Urgency: Critical. An inverter fault means your load is unprotected. Contact a qualified Eaton service technician immediately.
Fan and Thermal Alarms
Fan Failure / Overtemperature
What it means: One or more cooling fans have failed, or the internal temperature has exceeded safe operating limits. If left unaddressed, the UPS will throttle output or transfer to bypass to protect internal components.
What to do: Check that the UPS ventilation slots are not obstructed. If airflow is clear but the alarm persists, a fan replacement is required. Fan failures on the 9PX are a relatively common repair and can usually be resolved on a single service visit.
When to Call for Service
Some alarms — like a routine Replace Battery warning — give you time to schedule a visit. Others, like an inverter fault or bypass alarm, mean your load is currently unprotected and require an emergency call.
As a general rule: if your Eaton UPS is on bypass, showing a charger or inverter fault, or alarming during a live power event, treat it as urgent.
Eaton Service Canada provides emergency on-site repair for Eaton UPS faults across Canada. Call 1 (438) 881-3363 any time or contact us online. For multi-brand emergency UPS repair, visit GDF Technologies. For replacement batteries, visit UPS Plus Battery.