Question Cpu fan and psu gets on immediately without pressing power switch

[jetuaime 81]

I have an i3 4150 pc with ecs h81h3-m4 motherboard. The psu fan and cpu fan (loud full speed) gets on as soon as i switch on the wall plug. The pc doesnt boot and only starts once i press the power button on the cabinet, the cpu fan also switches to normal speed and it sort of works fine, i have just tried 10mins or so.

I have found that the 4th pin (ps_on) on the motherboard power connector is giving 500ohms vs ground; on a good motherboard its showing open and im guessing this is the problem. Anyone has a circuit diagram or hint what could the problem be?

 

[jetuaime 81]

I have an i3 4150 pc with ecs h81h3-m4 motherboard. The psu fan and cpu fan (loud full speed) gets on as soon as i switch on the wall plug. The pc doesnt boot and only starts once i press the power button on the cabinet, the cpu fan also switches to normal speed and it sort of works fine, i have just tried 10mins or so.

I have found that the 4th pin (ps_on) on the motherboard power connector is giving 500ohms vs ground; on a good motherboard its showing open and im guessing this is the problem. Anyone has a circuit diagram or hint what could the problem be?

Well i guess i was wrong, i saw another board giving 700 to 800 ohms 4th pin to ground and its working fine. I am lost.