If that pin is burnt and knackered as that, then the socket is likely knackered as well to the degree that if you put a new relay in, the arcing will burn the pin off the new relay too!
If you don't know what it does and you can't find out by switching things and watching things then............
1) make a note of the number of wires on the relay base
2) make a note of the colour of the wire and any tracer colour too and which pin number that wire goes to.
3) Look at your Haynes electrical schematic at all the relays in the circuit and compare your wiring and colours on each.
4) By this process of elimination and matching you should find the closest fit.
5) when you find the one you think it is, check whether this function on the car works or not assuming it is one that shows easily before ordering your new relay
& base.
:wink ::shock: 
