Auxiliary power led is amber on my dell dimension E520 is amber and it wont boot

I have a Dell dimension E520 which has not been working for some days now. When i pressed the power button the power led shows amber and blink for 3 time and goes off, I changed the memories but still the problem exist. Also on the mother board the auxiliary power led show amber.
when I pressed the power the fan also starts and goes off in just 2 seconds
please I need assistance

This is a Power Supply issue 9 times out of 10.

I'd replace the Power Supply, it's cheap and easy to replace, and if you get the same result (amber light) then you'll know for sure that it's not the power supply, in which case it's likely to be the motherboard.

However, in my experience fixing Dells, blinking Amber is almost always a Power supply issue, either that or it's not grounding out right, but I'm assuming you've already tried unplugging it along with any surge protectors, and than retried?

EDIT: And be sure to remove any USB devices, as those suck power, even when it's off.