Data Centers

Wake On LAN setting causes PC to mysteriously power on

When a powered-down PC began to mysteriously turn itself back on, the troubleshooting tech turned to our Technical Q&A for help. Find out how members were able to stop these phantom power-ups.

Following logical troubleshooting steps is usually an effective way to get to the bottom of a system malfunction—but you may want to eliminate a few obvious possibilities first. As one TechRepublic member discovered, before concluding that a component has failed or that a virus has struck, it makes sense to check a system's settings to ensure that it's not actually functioning by design.

A PC with a mind of its own
Writing in our Technical Q&A forums, member D & R was puzzled by the behavior of a client's system. The system was running Windows 2000 SP3, and D & R reported that it had plenty of RAM and drive space. The problem occurred after the system was shut down. D & R said that after normal shutdown, the system would automatically restart itself sometime later.

D & R wanted to know what could cause this behavior, and TR members responded with a number of tips that helped isolate the source of the problem. In D & R's case, the "problem" actually turned out to be a system setting, but the information that members provided is still helpful in diagnosing and fixing a variety of issues.

Power switch or supply could be to blame
Charlie Harag, technician for Smiths Aerospace, identified the power switch as one possible cause.

"Since the ATX power switch is a simple momentary contact push button switch," Harag wrote, "they can fail and complete the circuit on their own."

To determine whether this was in fact the problem, Harag recommended disconnecting the power switch cable before shutting down the system. If the system still restarted itself, a failed power switch would obviously not be the cause of the behavior.

Harag said that another possibility could be a failed power supply control circuit.

"An ATX supply is on all the time. It switches to full on when instructed to do so by the motherboard," he said. Diagnosing this issue would require replacing the power supply.

He added that a problem with the motherboard could cause the system to restart itself. Too much current on the standby line could be the culprit.

External threats
Ladytech suggested checking the system for viruses, Trojans, adware, or spyware, any of which could have the computer automatically start up. In addition to running a virus check, Ladytech said D & R should use Ad-Aware or SpyBot Search&Destroy to find and remove adware and spyware.

Wake On BIOS setting is the cause
Harag also suggested checking the system BIOS setup. Wake On event settings under Power Management are usually the cause of automatic restarts. Ladytech agreed that the real cause of D & R's problem could be the setting for either Wake On LAN or Wake On Modem. Both members suggested disabling the Wake On settings to prevent the automatic restarts.

D & R followed up on this possibility and discovered that the system's Wake On features were indeed activated—and disabling them fixed the problem.

Eliminate the obvious
As these member suggestions show, a number of factors can contribute to automatic system restarts and other aberrant behaviors. So before launching a full-scale troubleshooting effort, make sure that system BIOS settings aren't the cause of the issues. If the settings are correct, you can track down the problem by running checks on components such as the power switch, power supply, and motherboard.

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