American Power Conversion MatrixTM UPS - Manual (Page 29)

7.2 Fault Messages
The UPS will display one of the below illustrated screens when a fault internal to the UPS has been detected. See
section 7.5 which covers obtaining service.
7.2.1 Replace Electronics Unit (EU)
A DC imbalance fault results in bypass operation - load power is lost during a utility failure.
Overheating within the EU results in bypass operation - load power is lost during a
utility failure.
Failure of either EU fan while operating on-battery may cause overheating within
the EU. Overheating while on-battery will result in the loss of load power.
Failure of either fan while operating on-line will result in bypass
operation - load power may be lost during a utility failure.
A battery charger fault results in bypass operation - load power is lost during a
utility failure.
A main relay fault results in loss of load power. Remove the EU to resume
load power in the bypass mode - load power is lost during a utility failure.
7.2.2 UPS requires service
The UPS may remain operating when this IU fan fault message is encountered.
Schedule UPS service when convenient.
Do not attempt manual bypass operation when this fault message is
encountered as load power will be lost. Schedule UPS service when convenient.
If the input voltage tap configuration has been changed, a qualified technician
should reinspect the connections - see section 4.5. An output voltage select
fault results in bypass operation - load power is lost during a utility failure.
A bypass relay fault will result in permanent bypass operation - load power
will be lost during a utility failure.