Laptop Fan Spins on Boot Test, but that's it.

[DejaVu]

It then gets stupidly hot and powers off instantly as it's meant too.
I know the fan works, because on occasion it spins right - just not very often.

It seems to me the motherboard is not letting the fan know it's getting hot in here.
Anyone else come across this? Or better still, a means to repair it without dumping the motherboard?

I'm getting some right crappy jobs lately!

It's an Advent 6650 (Go figure!)

--UPDATE
Tested the fan on a AA Battery to make sure it would spin. Being only 1.5v it spun slowly, but it did spin. Fan seems fine.

Is there a thermal fan switch on motherboards or is it controlled by the CPU?

[big3card]

cpu or bios ive always assumed

[DejaVu]

'Solved' this one if anyone's ever interested.

Screwing the CPU down into place stopped the fan spinning - tested this while it was all switched on as a last resort.
Removed what can only be described as debris (Crisps, Finger nails, dried jizz) from under the Motherboard.

Perhaps earthing out from the CPU screw point? Not even sure. Main thing - it's fixed.