I have several of these relays for sale. They allow you to change your wipers from having a single fixed intermittent time, as came standard, to being able to program the interval, from about less than one to 30 seconds. 

You simply remove the relay numbered 19 and replace with this relay. They will work on any Vanagon which already has the fixed intermittent feature (meaning your wiper stalk goes in the down position to set to intermittent. You simply move your stalk down then immediately back up, then wait your desired interval time, then move it back down to intermittent. It will remember that interval until you change it.

I have read that there are some early Vanagons without the intermittent feature at all, to which you can add the feature by removing a stop in the wiper stalk. These relays should also work for those Vanagons as well. 

They are good used relays, sold for $20 shipped in the U.S. If you're outside the U.S., I can ship for whatever additional cost it is to your area. If you find someone else selling the same relay for less, let me know and I might be able to match the price. They are used, so I can't offer a warranty other than saying that if you try it within a few days of receiving it and it doesn't work, you can return or exchange it. I've sold several in the past and haven't heard back with any problems. 

Ed