Wow. Pigs and trafficators, who'd have thought. I guess that way one could be warned which way that road hog is going to turn. Maybe send a picture of the relay, but otherwise, I'd say try all the combinations of pin pairs, including the case as ground, and listen for the click of the relay. Check the other terminals for continuity. I'd say put that right in series with the PWM interruptor on that "brown" wire. Now you got dancing pigs like HEE HAW. Attach a picture or a video when you're done. I'll give you an address for some of that Windshield Wiper Meat when it's done.