Hi,
ASR-9006-FAN is EOL announced and replacement part is ASR-9006-FAN-v2.
https://www.cisco.com/c/en/us/products/collateral/routers/asr-9000-series-aggregation-services-routers/eos-eol-notice-c51-737924.html
normally, new product is releasing with several improvements. FAN modules are not affecting to network traffic directly but adversely under different circumstances. such as , if fan module not working, device heat is getting high and device may reboot.
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Good luck
KB