MacBook Air 820 3437, just stopped working, fan spin, seems to be switching on, but.

[leonattpcs]

No battery connected, connect power to the board in computer, no happy tone nothing on screen, get green then red light so seems to be charging.
Fan spin all ok, but nothing on screen. Hold down power button and fan stops spinning as though it is switched on like usual and just switched off.
Take board out, connect power, fan spin then gets faster, understanding this to be normal with nothing connected to board. Looking at board, just dust, no liquid damage, no external clues on computer. Poking around board for voltages, have seen most there, not seen all yet as have not checked thoroughly.
Knowing the issue up to now, does anyone have any clues as to what to look for?
Thanks

 

[2informaticos]

Try to confirm USB activity.
Does the board restart two times before stays on?

 

[leonattpcs]

No, when connecting power, the fan starts to spin and keeps spinning. I know from experience, it does the on off thing before staying on. USB activity? I will see what I can find from the ports etc...
Thanks

 

[2informaticos]

Try new BIOS, with clean ME.

 

[leonattpcs]

How is the bios cleaned? Removing the chip?

 

[2informaticos]

Pull off the chip and use external programmer.
Unless you have Medusa which can do it onboard...

 

[leonattpcs]

No medusa no. Will look at usb function first

 

[leonattpcs]

No USB function. With power connected to board and fan spinning, connected usb mouse, no light coming up on the usb mouse no nothing happening on usb.