Dell Dimension C521 intermittent error light 3

[Stu]

I have a Dell Dimension C521 that has suddenly developed an intermittent problem where it will not boot but display the number three error light. If I switch it off and on again, it will normally boot OK. Then maybe the next day when I come to switch it on I will get the error light.

I have looked the code up in the manual and it points to a possible CPU fault.

How likely is it to be the CPU? Could it be the motherboard or something else entirely? I've already checked the RAM, this throws up no errors whatsoever.

 

[NYJimbo]

Observe the cpu fan when this happens, see if its spinning. Sometimes a machine will die as soon as it detects the cpu fan not working, not sure if this unit will produce a CPU fan error or cpu error. Sometimes a restart on a stuck fan will get it going.

This machine has a special PSU, but if the wiring is all the same I would try to cable in a generic PSU temporarily and see if the problem goes away. The PSU could be failing. I have seen them do this when they are cold.

A real CPU error that is not power or thermal is usually a permanent error, not something that might not work randomly on boot. I would suspect other things, but if you got a spare AMD processor laying around..........