I can't say that I've seen this behavior. Let's see what we can find :
Fan is on; Do we have display? If yes, can you go into the DSP and change settings? I suspect you can.
Now that we've done this look around, we will have to go inside. Do you have technical abilities? Can you use a meter? Do you understand electronic circuits?
In the '3' range, it has to do with the 'Ruby' chip on the main board;
In the '4' range, it has to do with the APM (display) module;
I don't have the current information for the '1' and '2' range.
In both cases, there is no user serviceable parts to access; However, by the looks of the problem, it may just be a bad regulator!