Siemens S5-135U/155U System Manual page 131

Fault Indications/
Power supply faults are indicated via relay contacts and LEDs.
Diagnostics
The following table shows when the relay contacts are open or closed:
Switched off
In normal operation
During fault
The LEDs indicate the following faults:
"Fan Fault" LED
lights up.
"Batt. low" LED
lights up.
System Manual
C79000-G8576-C199-06
Central Controllers and Expansion Units Power Supply Units
Power Supply Relay Contacts 1-2
Open
Closed
Open
LED
A fan fault has occurred.
The battery voltage has dropped below
2.7 V.
Relay Contacts 2-3
Closed
Open
Closed
Cause Action
Replace fan
Replace backup
battery
4-65