I'm hoping someone here can help me think through a puzzle I'm working on here. I've got aftermarket fogs and driving lights installed at the moment. Right now, I use a 3-position switch (on1, off, on2) to control them. I just got a factory fog switch (thanks brandoncrone! ), and I want to use it to control both of them.

 

In a stock setup, the fogs go off when the highbeams go on. I'd like to sort of replicate this, by having the lights switch from fogs to driving lights when the highbeams come on (and more importantly, taking the driving lights off when the highbeams are turned off). I'm guessing that I can tap the highbeam and lowbeam wires, making them the grounds for the relay (pin 85/86). A third relay would be the "master" relay, sending power to both fog and driving relays whenever the foglight switch is on.

 

 

Attached is an abomination of a wiring diagram. Is it going to work??? I guess I don't full understand how the ground on the highbeam/lowbeam gets switched.

Provided the factory setup does apply +12 to the high and low beams and grounds the other side to turn them on, then it looks like your setup should work.

 

Here's an alternative setup that still uses only two relays: (again I don't know if the factory setup grounds the bulbs to turn them on):

 

edit: oh yes if you have daytime running lights that might activate the driving light relay as well.

Thanks for the advice. On my model year anyway (with high and low beams on the same lamp), it's definitely the ground that switches. I don't know why it didn't occur to me that that first relay in my diagram is pointless.

Porcupine's diagram will work perfectly, however have you considered getting another switch? I would leave them separate so I could switch the fogs with the parking light in order to have them on without the headlights.

I know the whole point of fogs is to not use your headlights, but mine just won't cut it at anything faster than parking lot speeds. I use them more in rain to fill in the side of the road and the area immediately in front the car (they're the "better" cheapy Hellas, little projectors that throw amber light).

 

But hey, while I'm doing wiring, I could just add another relay on the parking lot circuit for the fogs...

 

(I'm going to need a relay box soon!)

yeah, I'm working on a new lighting/electrical setup. Upgraded headlight wiring with relays, room for a second set of FF1000 driving lights, and possibly some fog lights to go in my new turbo bumper. With my supertones that will make for 6 relays.

 

I intend to build a relay/fuse box for all this stuff and place it behind the pass headlight, and run a big wire straight to it from the alternator.

yeah, I'm working on a new lighting/electrical setup. Upgraded headlight wiring with relays, room for a second set of FF1000 driving lights, and possibly some fog lights to go in my new turbo bumper. With my supertones that will make for 6 relays.

 

I intend to build a relay/fuse box for all this stuff and place it behind the pass headlight, and run a big wire straight to it from the alternator.

I like that idea (I've got my eyes out for some new horns on craigslist myself). One wire would be simpler than the rat's nest I currently have coming off the positive battery terminal. I'll have to swing by my electronics guy to see what he's got in the way of relay boxes. 6 is probably a good number - room to grow, and all.