[ubuntu] Dell Inspiron 7559 - fans run constantly

I have a new Dell Inspiron 7559. This has the newer skylake core i7. It also has an nvidia 960m with optimus.

Under Windows 10 the laptop stays nice and cool. The fans hardly come on, even under a load. When they do come on, they shut off quickly and the temps drop.

Under Ubuntu (or any Linux I've tried), once the fans start, they run pretty much forever. When the laptop is cold, and I boot into Ubuntu the fans are off. However, after a few minutes as the laptop warms up, the fans will kick on and continue to run at the slowest speed.

Thinking since it's a newer skylake CPU, I've tried every Ubuntu mainline keel (4.4, 4.5, 4.6rc1). I've also tried Arch Linux, Manjaro, Linux Mint, etc. The fans continue to spin.

The one thing I did try that finally made the fans stop was disabling the nvidia GPU with bbswitch, taking the bottom off the laptop to increase airflow, and opening a window in the room to lower the ambient temperature. However the fans still run for about an hour once they start. Also watching the temps with lm-sensors, it seems like when the fans do shut off, it's when the SODIMM temp gets to 39c. However, the 39c temp is never reached under -normal- conditions. (i.e with the bottom cover on in a warm room) CPU temps are always well below 40c when the fans are ruing.

I would assume there is some hardware issue, or something is heating up. But then why does it work flawlessly under Windows?

So, anyway, I'm throwing this out there in case anyone has some thoughts or ideas. I've pretty much exhausted all of my know-how and I am at my wits end.

Help?