Let me try a word-picture. The system on my coach is a Series 610 and my coach has a build date of 5/98, so here goes. Starting at the entry door. The first removable panel has a clear plastic loop to use for leverage in pulling it out. The next panel to the left is shaped somewhat like a 1/2 circle and is removable one the 1st panel is out. This gives access to (amoung other things) the HWH "brain". This is just to the left of the opening. There are two alumnium boxes, one on top of the other, with the bottom one on the floor. These two boxes look to be about the size of the box of an electric wall switch. There are a mumber of fuses here as well as a circut board.
I don't think this is where the device is that determines what "level" is, but is where that device sends output for telling the controller what to do. It was one of the fuses in this area that got toasted.
Now, there is another fuse box near the right wall that has accessories and there are fuses there as well that are involved in the HWH system, at least that is how it looks.
Hope this helps.
'99 Alpine Coach