Never had an issue starting the van for the past year

Now in the last few weeks, about 30% of the time, I turn the key and when I get to the ignition position, the power (including dash) turns off. Then I try a few more times and it eventually works.

And in the past couple days, 100% of the time, I turn the key and when I get to the ignition position, the power (including dash) turns off. The power remains off when I try again, and turning the key does nothing. All power in the van seems to be cut. Some time between a few minutes and 24 hours, it will come back enough to turn the key and hear the buzzing/see dash lights, and then it will cut out again.

The battery is only about 18 months old and the contacts are clean (I'll get it tested tonight anyway.) Any thoughts?

 

I would be looking at the ignition switch itself unless you recently replaced it. The switch is almost 20 years old and getting worn and tired. Replace the switch and see what happens unless someone else has a better suggestion or reply. Just my 2 cents worth.