Not sure what you mean by 'connections in the box'...........
When I discovered mine not working I went through same fault finding process replacing fuses, putting in new switch - but ended up (some 2 years later!!) sourcing unit from breakers yard.
When I got the old motor out the operating spindle (bit wiper connects to) was seized solid. I gave it to a chum who enjoys challenges a few months ago - and said see if you can sort this one out and it doesnt matter if you break it. Must chase him up - thanks for reminding me!!
It is my view water leaks down the spindle and if you have not used your wiper for a while the corrosion produces enough 'stiction' to prevent motor operating. If you do without for a while (in my case 2 years) it is then well and truly seized together.
If they worked on you cars recently take them out and get them on the bench you may be able to save them.
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K