Computer instantly shuts down if network cable connected

Question

We have a Pentium 4 PC in the office that has recently started shutting down a couple of seconds after a network cable is connected. It isn't software related, as the PC also shuts down before it POSTs when turning it on if a network cable is connected. It does not shut down gracefully... it just switches itself off.

If the other end of the network cable is not connected to anything else, the PC will not shut down (it continues to function fine).

The problem happens even when a different network cable and outlet is used.

What could be happening here?

Solution

With no cable connected, can you run high-resource demanding applications ? If you can, then your PSU is ok. If PC crashes, then it's your PSU ar fault.

From your description, sounds like theres a short-circuit on your network interface card. So it's best that you change your NIC or add a PCI one if you're using the on-board.

An exception to this is if the network youre using has PoE. That will make 4 of the wires in the network cable provide power, which can also cause a short-circuit. But this is a rare situation. Outlets should not provide PoE.

Comments

[Peter Fowler]

Assuming the Ethernet port is on the motherboard, I would guess that it has failed electrically. If it is a desktop then you could try fitting a new Network Interface Card (NIC) as they are fairly cheap.

[Thalys]

Sounds like something is... to use the technical phrase, borked. I'd inspect for bad capasitors and other obvious damage to the board if its a desktop. Using a replacement NIC is probably a good idea if you need to keep the old girl running.