Narcoleptic G5s (#2): Bad hardware?; potential workarounds

Narcoleptic G5s (#2): Bad hardware?; potential workarounds

We continue to cover an issue where some G5s fall asleep right after waking up.

Bad hardware? A new thread regarding a similar issue has popped up on the Apple Discussion boards. In this case, G5s are falling asleep during normal usage, apparently due to a thermal management issue. Users experiencing the issue report the string:

"PowerMac7,3 Thermal Manager: Thermal Runaway Detected: System Will Sleep"

appearing in the Mac OS X console.

One poster writes " Dual 2.5 just came back. Appears problem was with one processor thinking it was overheating even though it wasn't, and the fans go nuts in response. Had the dual processor unit changed and last I heard he said it was running ok. I think that the problems are due to a rogue faulty batch of G5 processors slipping by testing/QA at the IBM factory."

MacFixIt reader Clark Jackson reports a strikingly similar situation "I had a dual G5 2.0 that was falling asleep frequently without cause. I finally tracked the problem down to a bad CPU. Running the hardware tests indicated the problem; boot from the CD (or DVD?) that came with the computer and run the hardware tests. One indication I had that the CPU was bad was that prior to failure one of the fans was running much more that it should have.

"Ultimately I replaced 3 burned up CPU?s; it was my mother board that was causing my CPU?s to fail. It must have been some kind of voltage regulation issue because after replacing the mother board the problem (of burning up CPU?s) went away."

Potential workarounds

Waiting for a full wake-up In many cases, as previously reported, G5s experiencing this problem will wake from sleep momentarily only to drift away in a matter of seconds. MacFixIt reader Marvin Sable reports that in his case, simply waiting for the machine to fully wake up before introducing any mouse or keyboard activity, caused the problem not to occur.

"I experienced the G5 suddenly and quickly returning to sleep mode after trying to wake it. I discovered that if I just hit a key and "waited" till it woke completely before trying to mouse or type, that it did not go back to sleep mode uninvited. "

Resetting PRAM A handful of readers have reported that resetting their G5's PRAM, as described in Knowledge Base article #2238, resolved the issue.

In order to reset PRAM, shut down the computer, turn it back on, then immediately hold down the Command, Option, P, and R keys until the computer restarts and you hear the startup sound for the second time.

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