wiper motor, do i need a relay?

A few months ago my friend picked up a '78 Ford Courier for a song. Truck runs great but the wiring/electrical system was a mess. We decided to buy an aftermarket wirning harness and install it. We also converted the truck to a 1-wire alternator, and it is doing great.

Now, we are trying to get the wipers buttoned up. Originally the truck had a wiper/washer/hazard/headlight switch mounted on the column. It was falling apart and wasn't working right. Since new ones are obsolete, we opted to put separate switches on the dash. Everything has worked out great except for the wipers. I've tried all kinds of different ways of wiring it up and I can't get it to work.

The wiper motor has four wires coming out of it. There is a blue wire, blue with a white stripe, blue with a red stripe and a blue with a black stripe.

The solid blue originally went to the old fuse box to the "wiper" terminal.

The other three went into the cab of the truck and plugged into the wiring harness on the switch. The blue/white wire is the "low" wiper speed, and the blue/red is the "high" wiper speed. I got the wipers to work with both of these wires by grounding them (which I thought that was strange). The last wire--blue/black I was trying to figure out, but I couldn't get to do anything. Would this be the "park" wire? I don't understand how to hook this one up. Midway through trying to figure it out, my friend's dog somehow got a hold of my test light and decided he wanted to use it as a chew toy, so the project has stalled out right here for now.  

I'm thinking I'm going to need a relay for this, but I have no idea how to wire it up. If anyone can help and possibly put up a diagram I'd greatly appreciate it. I really need to get this Courier project wrapped up. Thanks in advance!      E

Read the entire following thread.  Pay close attention to the post that opens up when clickiing on the link.

https://www.the12volt.com/installbay/forum_posts.asp~TID~116752~KW~wiper~PN~0~TPN~2#568845

I do not know if it is polarized as yours, but it should at least help you to understand how the park wire works.  Your motor may be all together different, but it might help you out.