Having exact same issues with palit and kfa2 1660s, did you find a fix? Tried everything you have already. They work when directly in the mobo.
Usualy a riser issue.
Check if their deliver pcie voltage.
Thanks for the quick reply. When I put both my 1060 or 1080ti in the exact same risers, the fans work. However put either the 1660 super palit or kfa2 in the same risers, the fans don't work. The 1660s work perfectly And get a hash rate of about 32 but the fans don't work at all... Its very confusing.
This problem occurs with 1660 super palit graphics cards. The culprit is the graphics card manufacturer, because 1660 super palit fans do not work in all raisers.
First, clean all raiser pins that come in contact with the graphics card and motherboard.
If this does not help, you will have to buy another raiser.
Try a 6 pin raiser, then a sata raiser