1999 Ford F350 Water leaking into glove box, truck computer

I have found my glove box full water. I cleaned the cowling of dirt and leaves and the rubber seal around the window but there still is water getting in somewhere. I saw a drop or two from the passenger grab handle when it was raining, but just once. I had heard that there is a wheel well that can get plugged and backup into the truck but I can't find any plug or if it is true. Also the ABS light comes on at times when I am driving. Additionally I have repaired all the vacum lines for the defrost and vacum pump but when the hubs are locked in then the heater selections don't work; the air goes to the defrost vents. When the hubs are not locked in the heater selections work. A mechanic told me that there is a computer on the passenger side that controls all these settings, so I am wondering if it got wet and if so can you please explain how to test it or remove and clean the contacts. I am hoping that just the contacts are contaminated (if this is the problem). Thank you.