85 E350 random brake dash light coming on

[Cubey]

Maybe the ball is the switch on vans? The hose leading off of the cruise servo has wires that joins it's path down, whuch you can see in the first part of the video.

 

[Selahdoor]

Looks like the wires that go to that switch are red and green. You have at least one red wire that runs down, way down, behind the battery on the driver's side.

If I had to give a WAG... I'd guess that your switch is somewhere down behind or beside the driver's battery.