I recently did this mod on my turbo, but I'm afraid I can't remember which colour wire on the socket tail was which.

But essentially the stock switch is illuminated to make it easier to locate at night, so from memory I think you'll find the top two connectors on the back of the switch are for the internal lamp which plugs into the switch housing.

I picked up a feed for this from the lamp feed on the cigarette lighter.

The bottom two connectors, again from memory, switch the

+12v feed to the rear fog on and off.

As you are only switching the

+12v feed for the fog lamp, it doesn't matter which way around these go.

If you have a multimeter it's easy to double check this on the switch.

What the stock switch doesn't have is a built in warning light, which I believe is strictly speaking required for the MOT, as I think this was fitted in the dash on UK models.

That said my turbo didn't have a warning light when I bought it, and had just gone through an MOT.

I've now fitted a small red led adjacent to the switch to try to avoid any future issues with this.

I also wired the switch to operate a relay, rather than switching the

+12v feed for the rear fogs directly as I wasn't sure of the load the switch could take, and thought it was better to be safe than sorry.

Paul