I know that the third terminal on a VW was used to park the wipers. Not sure how it worked but that is what the schematic says.
If you have a photo someone will be able to tell you if it is stock chevy. You can also go to one of the (auto-discount-oriley-quest-zone) sites and look at some of the suspected models, that is if you have a clue what the wiper motor might be.
You can link a digital photo by putting it on one of the sites that host photos webshots, photobucket, etc. Then cut and paste the address into your reply.
There is a tech help on how to do the photos in IT short bus on this site.
Good luck
