Any ideas what the switch on the left is for. Been playing with it for a while now, seems to make no difference.

 

doesn't look factory. have a look at the wiring and connectors at the back of the switch...if it pokes thru the firewall by itself, its aftermarket. any after market lights installed?

 

Follow the wires. Definitely not stock.

 

The only aftermarket lights there were I personally uninstalled because they were old and faded "fog" led lamps. Took a look too see just now, they were tied into those which were on a separate switch of another style entirely on the other side of the column. I think, maybe, that switch operates the actual stock fog lamps next to the turn signals.