Ask Dave Taylor: Tech and Business


Why is my PC power supply randomly shutting off?

The power supply for my PC intermittently, and for no apparent reason, shuts down completely (no voltage on PS-ON). When this happens, if I immediately cycle the power switch on the power supply and then press the on/off switch, the computer starts normally. However, if this happens when I am away from the computer and everything has had time to cool, the above procedure does not work. When I attempt to start by using the above, the panel lights flash momentarily and the power supply shuts down again.

The only way to get it to start is to run a hair drier into the power supply fan for a few minutes, and then it will start. I don't think that it is anything in the power supply that needs to be warmed, but probably something else. I have disconnected everything connected to the motherboard, but nothing makes any difference. It would appear that the power supply is bad, but this is not the case, as I have replaced it with a known good unit, and the problem remains. I would certainly appreciate any help.

This is definitely not my area of expertise, so I asked my friend and colleague Jerry Foutz, who is a power supply guru, about your problem. Here's how he responded...