NEC 140He - Manual (Page 219)

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FAN Fault Lamps
FAN Fault lamp is adjacent to each fan module. These lamps are triangular in shape and point to their respective fans.
When the cooling fan is working normally, the lamp does not light. When a fan is not working normally, the lamp lights
in red. A cooling fan failure is also indicated by the status lamp located on the front panel. The failed fan may be
hot-swapped.
IMPORTANT: Do not remove a fan that is normally operating. Ask your service
representative for replacement of the cooling fan. If a cooling fan fails, do not continue to
operate the system, but ask your service representative for replacement as soon as you can.
FAN Fault lamp
FAN Fault lamp