CPU Fan starts and stops constantly. No Post

This morning my PC stop working. All leds and peripherals seems to be running, but the CPU Fan starts and stops spinning every several seconds and it don't post.

Relevant Specs:

Asus M2N-SLI
AMD Athlon64 X2 6000+
PSU C3 Tech 500w
4GB DDR2 800MHz
ECS GeForce 9600GT Accelero

Tests done:

- Turn on only Mobo and CPU. Same result.
- Tested with a old generic PSU. Same result.
- Tested the CPU Fan on Chassis fan header. It spinned normally. It seems not to be the CPU fan issue.
- Tested Chassis fan on CPU fan header. It spinned normally. The chassis fan has only 3 pins the header has 4.
- Tried to reset CMOS. Same result. Someone recommended me to let the jumper 8 hours on clear position, I will do it tonight.
- Both PSU works in another PC.
- Tested Fan without CPU. Same result.
- Tested CPU without Fan. Same result. It heats.

Posibilities:

- PSU failing in my system.
- CPU died.
- Mobo can't manage CPU fan.

I tested it without any peripherals, Mobo and CPU only, with no result. I suppose if the problem was in video board or memory stick the CPU fan would spin without these itens.

if you're still having problems, try posting another thread, since this one seems to have been seen only by me

I agree, it's likely the motherboard.

It sounds like you've eliminated everything else.

It's probably the Mobo. I bought a new PSU and the issue persists. I will try to trade it for a Mobo.

I should be the mobo almost for suer, so if that mobo meets your requirements, it was the only solution.