Switch S4810 dudas Power Entry Modules

Saben por que en un power supplies puede salir en su fanstatus la palabra absent?

SN03# sh version
Dell Real Time Operating System Software
Dell Operating System Version: 2.0
Dell Application Software Version: 9.9(0.0P1)

System Type: S4810
Control Processor: Freescale QorIQ P2020 with 2 Gbytes (2147483648 bytes) of memory, core(s) 1.