Little Black Box (83 King Cab)

Trying to troubleshoot a no tail light issue. While testing the link at the fuse block I wiggled the fuse hearing a clicking every time the fuse made contact. I pulled the passenger seat and found a little black box making the noise.
Called the local auto parts store and even the dealership with not luck from either place.
I am just trying to find out if this box could be the culprit and what the part is called if not, what are some other suggestions?
I have checked the fuse box & it gets power there as well as all the way too the box, but there is no wires running from the box only 1 connector to the box.

I would check your relays. I have an 87 and when the starter relay went out I just jumped it with a piece of wire. After doing so I had no headlights or tails. I unplugged the smaller plug from the starter relay and everything came on. Hope this helps.