Fans still not spinning on laptop even after replacing Mobo

Following on from THIS post, I have replaced the motherboard in said laptop.

Still no fans are running.
The fans' bearings aren't shot as I can freewheel them with my finger.

There are 3 fans in total.
One is the CPU fan which is plugged into one connector on the motherboard and the other two are mounted on their respective graphics cards on an "SLI module" which is plugged into a different socket on the motherboard.

Does anybody have any ideas?

I am about to dismantle the thing again to try and measure the resistance across the fan's terminals.
I shall also determine whether there is any voltage present at the connector (I can only measure the CPU fan connector voltage as the SLI GPU connector is very dense and tricky to get to).

I am thinking that either the new motherboard has the same issue as the previous one and that this is an inherent problem causing the new mobo to fail in the same manner (I was told it was brand new and faultless) OR all fans have coincidentally failed in a short space of time.

Thank you for any help

I am assuming that the machine does not boot.

I would suspect the CPU.

I have just been through a similar experience with a Dell Precision M65. Overheating and randomly shutting down. Cause was probably a fluff/cat hair blocked heat-sink.

Then one day after an unexpected shutdown, no fan, no video, no boot on power up. (fan tested as OK)
Swapped Motherboard - the same.
Swapped processor all OK with both motherboards.

Tim

Also check ram. A dead stick will stop a laptop going anywhere fast if the first module is dead but the second works. That was the case when I tried to upgrade 1 of my sticks of ram on a D810. It just sat there on pre bios logo / blank screen powered.