Wow, over 20 days without a post, and I didn’t notice. Yes, I’m still here… though not that much “here”, but offline. Here’s some of what happened.

About 5 months ago I posted about my temperature problems with the hard drive inside the iMac G5. I’d solved them somewhat preliminarly by buying a new (and supposedly less-hot) drive and putting some heatsink paste under the thermal sensor. Here’s the sensor picture again:

Well, about 3 weeks ago I left the iMac overnight, downloading some large file. I came back to it in the morning and it had frozen, and I heard some faint beeping which appeared to come from the UPS I keep just behind the machine. I turned everything off, waited half an hour or so, and restarted – everything worked fine but in two hours it froze again when the faint beeping started. This time, I could ascertain that

1) the beeping was actually a buzzing coming from the hard drive

2) the hard drive sensor said a reasonable 53.5C

3) the hard drive SMART sensor said the drive was actually at 61C!

Whoa. Something clearly had changed since February, when I said the average difference between the two sensors had shrunk to 4C. I did some cautious testing over the next week. Indeed, the external sensor never went over 53.5C – and the fan begins to rev up only at 54C, but it never got there. The sensor actually tracked the SMART value reasonably well – to 1C below 50C, to 3-4C until 53C, but then the internal temperature just soared. As soon as that went to anywhere over 59C, the drive froze and started buzzing. After cooling off everything started working again.

Up until last weekend, I tried changing the heatsink paste – no change. I tried out several fan control programs, none worked with the iMac. I tried finding out some software way to kick the fans up, but didn’t have too much time to really study the problem. A friend gave me a small flat fan from a laptop which I tried to mount inside, but there’s no space available anywhere near the drive.

About the only thing that helped a little was mounting a couple of other small fans blowing into the air intakes below the iMac – I glued them in place with some gaffer tape and ran them off a spare 12V supply. But it clearly wasn’t a definite solution; it sort of worked for a few hours as long as I kept the CPU speed on “reduced” and didn’t open too many programs at a time. I suppose someone should make a supplementary fan unit sucking air out of the iMac, like we had for the MacPlus… I wonder if the current Intel iMacs also overheat?

Anyway, last weekend I gave up and performed minor surgery on the sensor cable, making it about 10cm (4″) longer. The main trick was to convince it to part company with its original mounting place – people who’d performed this procedure before recommended using a “thin blade”, but none I had were thin enough. The optimum solution is a length of dental floss. If you try this, work it under the double-sided white tape that glues the sensor board to the metal bracket, so the tape stays stuck to the board. I got it off cleanly with its adhesive properties still intact.

I experimented with a few locations, but the only easy one was a small flat space between the drive spindle and the PC board. In that location, so far as I can see, the two temperatures track each other to 2C – usually even to 0.5C. One shouldn’t check the SMART temperature too frequently or the drive never sleeps; 20 minutes seems OK. The temperature hovers between 52C and 57C under normal workload… still not ideal. But the fans kick in and the iMac now sounds louder, much like it did when it was new. I suppose I’m the only iMac G5 owner who’s glad to hear loud fan noises…

However, today, just when I was finally ready to start working on my usual stuff again, the @#$%^& thing froze again – and while both temperatures were at 52C, where it should work. So either I need to reformat, or install air conditioning, or get a new drive while the current one is under warranty. Or all of these. There goes another weekend…