PowerMac G5 startup failures, red LED behind processor
I have a PowerMac G5 dual 2.5GHz machine, which was put into service in December 2004 and has basically been running non-stop since, with the occasional break for an upgrade or to fix a problem (I have a small marketing consulting business and this is my primary work machine). Recently, after installing a routine upgrade to Safari, the machine started refusing to restart. It started after the Safari upgrade; the upgrade finished, I told it to restart and I left the room. I came back to roaring fans and nothing on the monitor. So, I powered it off and waited a couple of minutes. When I tried to power it back on, I got the boot chime, a little fan noise and then silence. There was a red LED, which appeared to be behind the processors, on. The white LED was also on. But clearly the startup was going no further. So I turned it off, unplugged it for 10 minutes (which is supposed to be how you reset the SMU on this machine), and then it started up.
But that wasn't the end of it...the next time I tried to restart the machine, it again refused, and again gave me the mysterious red LED behind the processors. After a couple of tries of unplugging things and cold starting it, it did finally come back up. I'd had problems with the original hard drive on this machine (it failed and was replaced after 2 years), so I ran diagnostics on the startup drive--no problems. Then I figured I'd zap PRAM. So I shut it down, and tried to zap PRAM on startup...but it wouldn't start this time, so I couldn't zap PRAM. Then I tried unplugging the machine, waiting a while, and starting up again--no go. And I couldn't get it to boot from a backup copy of the system on an outboard firewire drive either. After unplugging everything, including the outboard firewire drives and all the USB devices except the mouse and keyboard, I STILL couldn't get it to come back up. Every time, the furthest it would get would be a grey screen with the apple on it, and that mysterious red LED deep in the bowels of the machine.
Finally, in despair, I brought it to the nearest Apple store and had a Genius look at it. After reproducing the problem (and finding NOTHING in the service manual about that mysterious red LED), he got the machine to boot from an outboard firewire drive running Leopard. He ran the disk utility and confirmed that my startup drive was just fine. He then reinstalled Tiger on my drive, and successfully restarted the machine. He then applied the Tiger combo update and--NO RESTART and no cold STARTUP (and that same red LED inside every time it failed). They couldn't zap PRAM. They even replaced the PRAM battery, but that didn't do anything either.
At that point, I left the machine with them so they could run Apple Diagnostics on the machine and see if there was a hardware problem. I was sure they'd find it was a processor gone up in smoke or something.
The good news is that there is a happy ending to this story. After running diagnostics and confirming that the hardware was just fine, they tried to zap PRAM. It didn't work; the machine wouldn't start. Then they reset the SMU, using the button on the logic board below the lower memory slots (apparently this button is on both the late 2004 and late 2005 PowerMac G5 models, which is not what the documentation says), then zapped PRAM as it was coming up, and lo and behold, the machine started! They then started and restarted it, and all was normal! I can confirm that the machine is now working properly--it starts, it restarts and it is working normally. The guys over at the Apple store were very patient, and this at the height of the holiday shopping season! However, they never did figure out what that mysterious red LED in back of the processors was, though one gentleman opined that it was probably just a light that indicated that it was stuck (well, we KNEW that!).
I still don't know what started this set of problems--clearly something got corrupted somewhere, or possibly multiple somewheres--but the combination of reinstalling the OS and resetting both the SMU (using the button) and PRAM seem to have cured it. I'm posting this in here, not as a question, but so that if anyone else runs into a similar situation, they have some things to try before throwing up their hands in despair. My next question? Why do these things always seem to happen when you're in the middle of some huge project 🙂 ???
But that wasn't the end of it...the next time I tried to restart the machine, it again refused, and again gave me the mysterious red LED behind the processors. After a couple of tries of unplugging things and cold starting it, it did finally come back up. I'd had problems with the original hard drive on this machine (it failed and was replaced after 2 years), so I ran diagnostics on the startup drive--no problems. Then I figured I'd zap PRAM. So I shut it down, and tried to zap PRAM on startup...but it wouldn't start this time, so I couldn't zap PRAM. Then I tried unplugging the machine, waiting a while, and starting up again--no go. And I couldn't get it to boot from a backup copy of the system on an outboard firewire drive either. After unplugging everything, including the outboard firewire drives and all the USB devices except the mouse and keyboard, I STILL couldn't get it to come back up. Every time, the furthest it would get would be a grey screen with the apple on it, and that mysterious red LED deep in the bowels of the machine.
Finally, in despair, I brought it to the nearest Apple store and had a Genius look at it. After reproducing the problem (and finding NOTHING in the service manual about that mysterious red LED), he got the machine to boot from an outboard firewire drive running Leopard. He ran the disk utility and confirmed that my startup drive was just fine. He then reinstalled Tiger on my drive, and successfully restarted the machine. He then applied the Tiger combo update and--NO RESTART and no cold STARTUP (and that same red LED inside every time it failed). They couldn't zap PRAM. They even replaced the PRAM battery, but that didn't do anything either.
At that point, I left the machine with them so they could run Apple Diagnostics on the machine and see if there was a hardware problem. I was sure they'd find it was a processor gone up in smoke or something.
The good news is that there is a happy ending to this story. After running diagnostics and confirming that the hardware was just fine, they tried to zap PRAM. It didn't work; the machine wouldn't start. Then they reset the SMU, using the button on the logic board below the lower memory slots (apparently this button is on both the late 2004 and late 2005 PowerMac G5 models, which is not what the documentation says), then zapped PRAM as it was coming up, and lo and behold, the machine started! They then started and restarted it, and all was normal! I can confirm that the machine is now working properly--it starts, it restarts and it is working normally. The guys over at the Apple store were very patient, and this at the height of the holiday shopping season! However, they never did figure out what that mysterious red LED in back of the processors was, though one gentleman opined that it was probably just a light that indicated that it was stuck (well, we KNEW that!).
I still don't know what started this set of problems--clearly something got corrupted somewhere, or possibly multiple somewheres--but the combination of reinstalling the OS and resetting both the SMU (using the button) and PRAM seem to have cured it. I'm posting this in here, not as a question, but so that if anyone else runs into a similar situation, they have some things to try before throwing up their hands in despair. My next question? Why do these things always seem to happen when you're in the middle of some huge project 🙂 ???
PowerMac G5 dual 2.5GHz, late 2004, Mac OS X (10.4.11), 5.5GB RAM
