Unexpected Power Down Of G4, PMU Responsible?

I agree the internal battery probably needs a replacement. I have a spare one I bought a while back which should be good, so I will swap it out when I get a chance!

I'll probably do more research this unexpected outage and see what I can find. If I discover anything useful, I'll post it here.

I replaced the battery last night, that issue is resolved. Please keep in mind I wasn't connecting the battery issue with a sudden shutdown, but that PMU message was the only indicator I could find that might explain why the system powered off suddenly.

Does the PMU determine if the system needs to power off in order to preserve the integrity of the hardware (e.g. processor)?

The power supply has already been replaced recently...the old one had a dead fan, which led to a lot of other heat issues that went away once I swapped it out.

The room the machine runs in averages 70 - 72 degrees F during winter, and 75 - 80 degrees F during spring/summer. Humidity varies between 40 - 60%. As far as I've seen from the operating specifications of the system, these ranges are acceptable. The room was around 80F and 60% humidity at the time I discovered it had powered off.

I run a quick open-case test about once a month to check for dead fans. Currently all are running. I also have an additional PCI fan that blows air out of the case.

If I have time tonight, I'll search the discussion boards (and Google 🙂 for any information I can find on unexpected power-downs for this type of system.

If the CPU is the cause, it is worth noting that I installed 2 GHz upgrade from Giga Designs about 2 - 3 years ago. If the problem continues/becomes more frequent, I still have the original heatsink and CPU that I could install to see the hardware is defecting, or if I've managed to accidentally smear the thermal compound onto the edges of the CPU itself (I had a Windows PC that kept "zapping" off because of poorly applied thermal compound).

Thanks for all the feedback, keep it coming!

Is your PSU's fan dead? As I noted in my post below/above, I had to replace that part a while back because the fan stopping spinning, leading to heat issues with the entire system. Surprisingly though, the system still ran for a long time until I actually noticed the problem! After that discovery, I decided to begin performing monthly checks of the fans by doing a quick open-case test with a flashlight.

Does anyone have recommendations on "mac friendly" temperature probes to install inside a G4? While I'm well aware of the environmental temperatures, I'm less aware of the true operating temperatures inside the case.

The closest I can get to getting a live sensor reading is from my HDDs via Temperature Monitor. I'm hoping someone knows of a good product that can be installed to monitor internal temperature (or connect to a CPU heatsink), ideally via software that understands how to communicate with the sensor.

A long while back I found an interesting mod article about a guy who replaced his internal speaker with a custom made holder for a simple temperature probe that he wedged within the heatsink, but that's beyond my interest in doing.

Thanks!

The issue resolved for me a long while back. I suspect the problem was having the UPS mistakenly hooked up to a special surge protected outlet. Once I replaced the unnecessary outlet with a normal one the system didn't exhibit the problem anymore.