I really hope you find some help here. I have the same machine, same problem. I'm about an inch from putting it out to pasture
whatever that means? Sell it for parts? I don't know what to do if it's completely dead. Anyway, it's so frustrating because I feel like the solution should be more clear. But it's not. And I've gotten a LOT of feedback.
I've been battling this for a year now. Last summer, my 3,1 had been acting funny: random reboots, random shut downs (no reboot), fans REVVING, non-booting. SMC resets wouldn't square it up, there in the "end". So, my clues were pointing to PSU. I replaced it and it ran like a dream, again. But only until recently. Now it's got all those same issues. Again. I've been pulling my hair out. Actually, I'm past that now, I'm more focused on an 'exit strategy'. But I got in touch with this guy on ebay that was selling power supplies. I asked him if a PSU could fail within a year, like this one may have. He said, "
I've handled hundreds of Mac Pro computers and your situation seems very odd. In my experience, the power supply is usually one of the last things to malfunction or go bad. That said, it's not out of the question
" Basically he dissuaded me from buying yet another PSU. But I still didn't have any answers.
I started
this thread on the Apple forums. One fellow there offered some things that seemed to be common fixes with other posters with similar symptoms:
I don't know what your solution will end up being, but I can give you a few ideas of what other Users have shared:
Dust Bunnies
disconnected cable to the temp sensor -- this will be detected by Apple hardware test
heatsink loose or off the "Northbridge" system controller, due to broken plastic screws
sloppy initial application of heat transfer compound at the CPUs -- (not likely, or your CPU temps would go nuts).
So, I was able to rule out: #2) Apple Harware test always says, "no problem found". I ruled out #3, Northbridge issues. It was good to go. Ruled out #4 because my CPU temps were just fine / normal. So that only left me with #1: Dust Bunnies. I was hopeful as it's great when the simplest / cheapest solution is the one that works. Canned air weren't enough for me. I bought a
HIGH-strength blower and cleaned it out. Sure a few bunnies blew free, but nothing too astonishing. Anyway, the machine did indeed work again. For a while. That very next power up was great! I let it run all night. It ran for 12 hours straight no issues at all.
But that was a few months ago. Slowly my issues have all crept back. I reseat cards, SMC resets. memtest says everything is a-okay. I'll swap RAM around. I'm at my wits end. (I bought a MacBook Pro last April and that plus a big bad NAS are likely going to be my way forward from here on.) But I'd love to figure out what's up with the Mac Pro. Now it basically will
not stay on. It maybut for no longer than 15 minutes. Sometimes it's very very slow to boot. Sometimes it will "double-boot" and get going. Sometimes it will turn on, but no boot chime. It will usually get going at some point, but in the end it's pretty much irrelevant, because minutes later it's going to power back down.
I don't know. I live on Maui. It's wet here. I run a dehumidifier quite often, but I've noticed a little corrosion on some logic board components
so maybe that's my issue. I'd love to KNOW something more definitive, but I don't think it'll come to that.
Finally,
here's one final thread I started. There's a link in it that will redirect back to a MacRumors thread because the OP there had seen this red light on the logic board that was suspicious. He never came to conclusion about what that light meant. I haven't either, as the ebay guy that helped me out, said he too had no idea what that light signifies. (It's not mentioned in the service guide. It's not really mentioned online that I could find.) In the MacRumors thread there, the dude finally concluded "I believe that led means the MP electrical management is not normal". But that's about it
Nothing completely concrete.
Good luck. I hope you can get it running again consistently.
