Hold on. You're could be falling for a trick I built into some of my cars for students to diagnose. With a poor mechanical connection at the fuse box, you'll still read 12.5 volts, ... Until you try to get significant current to flow through it, like when trying to supply ten to 15 amps to a starter solenoid. This would be like saying you have good water pressure at the nozzle at the end of a hose while you have that hose 99 percent blocked by standing on it. It isn't until you open the nozzle and try to get water to flow that you'll see the pressure drop to almost nothing. I suspect you are right that the connection is okay, but we don't want to overlook something stupid. Measure that voltage again when current is trying to flow. Either turn on the head lights or have a helper try to crank the engine.
I didn't bring this up earlier because it doesn't relate to part of the symptoms, meaning the engine that stalled while driving, but by the mid 2000s almost every manufacturer had complicated their starting circuits unnecessarily by adding a computer to the neutral safety switch circuit. In the past, with a weak or run-down battery, the engine would crank slowly or you'd get that chatter from the starter relay. Today, a weak battery, or a less-than-perfect connection, can cause a voltage drop just enough that the neutral safety circuit does not turn on to allow the starter relay to be turned on. The confusing result is we don't get the rapidly-clicking or buzzing relay any more. We get nothing.
The next thing is everyone has gone from a neutral safety switch to a "digital range selector". On the F-150 that is simply a set of four switches built into one assembly that goes in place of the older neutral safety switch. I'm not sure if that is what is used on your van. Some vehicles use a range sensor, identical in operation to a throttle position sensor. 5 volts or 12 volts is applied to one end, then the signal wire picks a voltage off of it relative to its position. That voltage only has to be off a little for the Engine Computer to think it's in gear and not in "park" or "neutral". That will inhibit the starter relay.
The problem is you really need a scanner to see what the computers are seeing to figure out a simple no-crank problem. The neutral safety switch or sensor will be listed along with its "state". Inputs are also shown. In this case, the "crank request" will be listed typically with something like "off", "denied", or a reason it's denied might be listed. If it never changes from "off", we would start by looking at the ignition switch and its wiring. The alternative would be to test the individual circuits and try to solve it that way. If it comes to that, I'll dig up a wiring diagram and figure out where to start.
Friday, December 2nd, 2016 AT 9:53 PM