Fix for heavy Kernel_task load on MacBook Air

UPDATE
In a follow-up post I describe how the kernel_task problem was solved.

First of all, english is not my native language. But those of you affected by this problem probably don't care. (I used Google myself to translate a Japanese blog post to troubleshoot the issue.)

My MacBook was delivered in early february '08, and worked fine until mid-summer. At that point I started having core shutdown-issues, that's when one of the two kernels in the processor is shut down to avoid over heating. After about two weeks I ran the Apple Hardware Test and found out that my fan was broken. The computer was brought to the firendly people at my local Apple Service Provider (www.dataservice.se) and got repaired in under three days. That's when the real problems started to occur.

Since mid-august the Kernel_task process has been at a constant load of >80% of the available free processor cycles, most of the time over 120%. I installed the iStat nano widget and it showed that though Kernel_task loaded the processor very heavily the computer ran fairly cool (about 40 degrees celcius at all measuring points). That, together with some googling, made me conclude that Kernel_task wasn't doing anything interesting, but merely reserving the cycles. Probably to prohibit any other process from doing real work, and thus heating the processor.

My attempted solutions have been many.
- I tried rebooting the computer more frequently (every day, instead of every couple of weeks).
- I installed the EFR-update for the Air.
- I reset the MBR.
- I used the MacBook Air on different surfaces (wood table, cloth, lap, lifted on som pens, etc.).
- with and without USB-disks, USB 3G-modem, Airport, charger, headphones, etc. connected.
But to no avail, the problem persisted, from booting the computer up until shutdown.

About a month ago I ran the Apple Hardware Test which gave me the following error code: 4SNS/1/40000000:TsOP-128.000

Googling it gave me a handful of hits, but only one with any kind of guidance. (That's the Japanese blog I wrote about earlier, which I unfortunately can't find at the moment.) He described my exact problem, and had his laptop sent to Apple for service. In a follow-up post he wrote that the service provider had swapped his logic board and made som firmware updates. But the problem didn't seem to have gone away. Another guy at the Apple Support forums have had the same Kernel_task issue and solution, with the problem remaining.

Today I went back to my service provider, the same one as last time, and explained my problem. I'll keep my fingers crossed and promise to do an update to this post when the little gem is back in my warm embrace!

My best wishes to those of you also affected by this problem!

Update
Here I describe how the solution worked to my kernel_task problem.