Intermittently-blowing fuses are by far, the hardest to solve. The goal is to get the problem to be there all the time so it can be diagnosed. A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it is not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.
As for the lighting problems, when there are so many different circuits involved at the same time, start by looking for what they have in common. The insane engineers at Ford have seen fit to hang an unnecessary, unreliable computer onto every circuit that never needed a computer before, and the result is exactly what you have. In this case it is the Body Computer we need to look at. Ford calls that the "GEM" module, (generic electronic module). In their pickup trucks, that module has a high failure rate from water dripping onto it from a leak by the windshield. I do not hear of those failures as often on the minivans. You will likely need to find a mechanic with a scanner that can access the computer and command it to activate the affected circuits. Doing that will help narrow down whether this is a computer problem or a problem with multiple wires.
Multiple corroded wires is a better suspect if the van has a trailer wiring harness that was spliced in with Scotch-Lok connectors. Those are fast, but they do not seal out moisture. The van's wires will corrode over time where those connectors cut through their insulation.
Monday, December 5th, 2016 AT 8:21 PM