Weird Electrical Problems on 03 Tahoe

[dabomb5756]

This isnt really tech, but it is a really stupid problem i've been having with an 03 tahoe.

The windsheild wipers will turn on, but wont turn off. The wipers do not pause, they are on low at all clicks of the switch, until you get to the highest, when they start moving quickly. If you try to turn them off, they will go back to low, but will not turn off. Turning off the ignition and accessories by pulling the key stops them wherever they are at instead of down positon.

The weird thing is that this only happens when the truck gets wet. Either through a carwash or in the rain of course. We have been pulling the fuse after it rains.
One more thing is that when it gets wet the horn gets funny too and will not work.

Any advice on where to start? The fuse panel is inside the cabin, so it should be fine.