One thing to check is are you using the latest BIOS, I'm pretty sure that Fan profiles are control by the UEFI/BIOS You won't find any setting for fan speed anywhere. If your on the latest UEFI/BIOS the perhaps a Re Flash might get them going for you. I assume they are clean and not blanked in with old dust.
G752VY-DH72 Win 10 Pro
512 GB M.2 Samsung 960 Pro
1 TB Samsung 850 pro 2.5 format
980m GTX 4 GB
32GB DDR 4 Standard RAM
Z97 PRO WiFi I7 4790K
Windows 10 Pro
Z97 -A
Windows 10 Pro