I'm sorting out the wiring in my 78 clubman resto and I'm stuck on one thing that isn't showing up on the wiring diagram.

There is a little cube 1" sqaure that is bolted in the engine bay next to the washer bottle. It has 2 earth and 2 live wires that plug in but I am not sure which way they go. I've tried plugging it in a few different ways but it doesn't seem to affect anything.

Could anyone tell me what it is, what it does and how do I plug it in?

Its a relay - designed to, when switched, give constant power to some electrical component.

Somebody should be able to tell you how its wired.

Mike