A relay is an option.
I use it for my old car and have done the mod a few times.
I laugh because it is the lazy way out. instead of taking the time to find the actual issue, I just bypass it permanently.
relay has 5 connections.
you have to read the relay to see how it is set up.
but basically you have the original power source. the one that reads like 10 volts from the wiring diagram that goes to that big splice of everything in the engine compartment.
I cut that line before the splice and make that the voltage that closes the relay.
other end of the circuit that closes the relay is just any ground. I usually wire it back to the battery.
The second circuit is power from the battery to the splice end that is hanging free now.
so when you hit the key, it gives power to the relay, closes the circuit and power from the battery goes to that giant splice powering the ballast, VR and alt, with full battery power instead of the 10 volts you had before.
I would get one that is waterproof but isn't 100 percent necessary as long as you hang it somewhere slightly protected behind the engine or air cleaner. not sure on a van.
there are some pretty cheap ones out there, but junk yarding that part is probably cheapest. you can probably get one for under 5 bucks at the parts store for a generic one.