I did not sleep well last night. The prospect of having to complete 3 translations on my backup machine (an old Titanium) while the MacBook was sent to repairs -for the 4th time- was not making me very cheerful.
I called Apple support this morning and they told me this fan problem could be triggered by static electricity.
The procedure to solve that is as follows:
- turn the machine off
- unplug it
- remove the battery
- press the start button for more than 10 seconds
- plug the machine and put the battery back
Command+Option+P+Rsimultaneously right after pressing the start button
The machine is supposed to emit 2 long beeps after booting and then starts normally.
I did not have 2 beeps, instead of that the MacBook entered a just as scary cycle of reboots. So I eventually stopped pressing the keys, and the machine decided to stop pedaling with my nerves and properly boot.
Now, the fan seems to behave properly. I'll hopefully be able to complete the jobs without having to send the machine to repairs... Only 5 months left on my AppleCare !!!