I have put a humbucker in my squier strat and also wired in a switch to tap it....I think.

I have wired it up so that the humbucker is separated on the 5 way switch (wired to position 3 and 5) which means that I can use it as a humbucker on position 4 or single coil on position 5. I have the middle pickup on an extra switch.

The problem is that it sounds great when I use position 5 (tapped) or position 3 (also tapped) but in position 4 it seems quiter which is the opposite to what I expected. When I put my multimeter on it I have found that the resistance goes down when in humbucker mode. Have I wired it up wrong?

The humbucker has 5 wires....

Uninsulated (Earth I assumed)

How should I do it?