How did you check CJB ( aka Central Junction Box , cab fuse panel ) fuse #11 ?
- Pull and stare at it, or check for + VDC on the pins on the back of the fuse while it was installed and the key in the run or accy position ?
The follow on test to this is to check the wiper relay socket for power with the truck in the run or accy key position
- powers pin #1 in the relay socket, meter from here to a know good ground like the battery neg terminal.
If this has + VDC on it, the fuse itself is fine and time to move on to an another test with the wiper relay itself ( if it is installed and you looked at the wrong position ) or the test the MFS.
There is no wiper run/park relay ?
- Are you sure about this, if so, that might be a good reason why the wipers don't work and would never work.
How did the installer come to the conclusion that you needed a new MFS ?
- Supposition and it just sounded good ?
Might want to pull the MFS and test it to see if you need to replace it before you go to a bone yard and buy another ( unknown if working ) MFS