Rear fog light wiring

'92 Si VTEC · Post by **jjmartin349571** » Fri Nov 14, 2014 9:53 pm

Really stupidly simple question that I should probably know the answer to, but if I'm wiring a rear fog light up does it have to be wired so that it can only be switched on with the lights?

If so, am I right in thinking I should take a feed from +12v, stick a fuse on and run it to a relay which is switched by a signal from the side lights, and then on to the fog switch, then to the rear fog, and then to earth?

I should know this

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Fri Nov 14, 2014 10:04 pm

jjmartin349571 wrote:Really stupidly simple question that I should probably know the answer to, but if I'm wiring a rear fog light up does it have to be wired so that it can only be switched on with the lights?

No, doesn't have to be. So long as it comes on and off for the MOT test, that's all they're bothered about!

if you did it that way though, at least it would stop you accidentally leaving the fog light on and running the battery flat.

jjmartin349571 wrote:If so, am I right in thinking I should take a feed from +12v, stick a fuse on and run it to a relay which is switched by a signal from the side lights, and then on to the fog switch, then to the rear fog, and then to earth?

That would work yes, but it's a bit of a gold plated solution.
You could just take a feed off the existing sidelight feed, because one extra bulb won't draw a lot. And then you wouldn't need the relay or additional fuse, because that circuit is already fused.

'92 Si VTEC · Post by **jjmartin349571** » Fri Nov 14, 2014 10:08 pm

Cheers Iain

Sounds like having a relay triggered by the sidelights is the way to go then, even though I could be lazy and still pass MOT. Why is it fused already though? I'd be taking a fresh feed from the fusebox.

Ah you got your edit in before my response

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Fri Nov 14, 2014 10:21 pm

Yeah, reading/writing while watching TV and drinking doesn't make for comprehensive understanding!

mercutio · Post by **mercutio** » Fri Nov 14, 2014 10:22 pm

no it ducking fussent

'92 Si VTEC · Post by **jjmartin349571** » Fri Nov 14, 2014 10:31 pm

As for my wiring conundrum, the idea of the fog light having its own circuit and fuse from the fuse box makes me feel all warm and fuzzy inside

So I'll probably use a spare slot in the fuse box and a fuse with a breakout cable to wire the fog in.