I recommend that you loosen and remove the screws holding the fuse block to allow better access to the wiring. It is very difficult to change wires on the back of the fuse block without doing this. Assuming you have a/c, you need to remove the screws and bracket that hold the relay installed on the bottom of the fuse block. In the picture, this is the relay hanging to the left of the brake pedal. I believe these screws also hold the fuse block, so once you remove them the fuse block should be more accessible.
One other thing to note. As I mentioned earlier, fuses 4 and 5 are tied together on the back of the fuse block. If you look at this picture Markos posted, you can see how that works. The connections for positions 4 and 5, before the fuses, are color coded red. On this block, there are two wires joined together in position 4, one immediately below the other. Referring back to the diagram, this corresponds to the two wires joined together in position 4. There is no wire in position 5 on this block, but if there were, it would have continuity with the wires in position 4. This is what I meant when I stated that portions of the back of the fuse block act as power distribution. In this case, unswitched power is distributed before the fuses across positions 4 and 5. Another reason this is important is that the exact positions of the wires does not matter. By way of example, the wire you are seeking might be connected to position 4 and it would function in the same manner as if it were connected to position 5.
Positions 6 and 7 are similar, with a solid green background. They act to distribute switched power.