best way to wire fog lights

[Handsdown]

i bought some crappy advance auto parts foglights and the diagram they give has a relay in the circuit... but it only comes with a fuseholder and a bunch of wires and a switch... it seems to be missing the relay that you hook the switch up to...

anyway what's the best way to wire foglights? are 2003 RS's prewired for fog lights?

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[brunetmj]

Well first you have to decide how you want them wired.
Come on with the low beams or do you want to use an independent switch? Yes the wiring exists for fog lights but here is the problem. After market lights are intended to be used with American cars. Subaru’s use a switch ground system so wiring has to be done differently.
Below is a diagram of how to use a relay and a switch. The diagram is mostly by satrya so I hope he doesn’t mind my posting it.

PM and give me a email adress and I will send a bigger shot than this one. Just ignore the word hella any relay and switch will do.

[satrya]

I'm not sure what extent of the fog pre-wiring is on the my2003 RS. If it is pretty much complete, minus the switch only, then you're in luck because the difference in switched ground vs switched positive would not be a problem. All you need is a compatible connector and simply use the lights and discard the rest from the aftermarket aux lights.

However, from brunetmj's description, I get the feeling that it is not this complete. Below is a slightly different diagram from the one recommended by brunetmj.

You will need to get a light relay (marked "Hella relay" in the diagram below). I believe even RadioShack may carry them. Just make sure the current rating of the relay and your fuse selection is compatible with the claimed wattage of the aux lights (roughly speaking, current_rating = claimed_wattage / 12V ; bear in mind that you need to add the wattage of both aux lights since you're only using 1 relay). If Radio Shack doesn't have any compatible relays, online places like digikey , parts express, etc. should have them.

Regarding the SPDT (--> 2 on positions with one button) switch in the diagram, this is so that the aux lights can be used either independently, or dependent on the high beams being lit (per US regulation afaik). If you just want to wire them independent of the high/low beams, you could just use a regular SPST (--> just one "on" position and one "off" position with one button) and forget the lower branch on the diagram that says "high beam switched ground".

[Handsdown]

okay great thank you!

[Handsdown]

it is complete except the switch, as far as i can tell(it's warmer today, got a chance to look and see.)

if this is true, i just hook the black wire up to the black striped wire(ground) at each light and the white(+) wire to the red striped wire on each side, and get the subaru switch, correct?

would it be cheaper to splice a dinky switch and a relay into the stock foglight switch harness? if so, what kind of relay, switched ground or +?

[satrya]

Originally Posted by Handsdown

if this is true, i just hook the black wire up to the black striped wire(ground) at each light and the white(+) wire to the red striped wire on each side, and get the subaru switch, correct?

Unless I misunderstood the statement above, you mean the pre-existing wiring goes even as far as the final connector that goes to the individual foglights. In that case, it doesn't matter which color of the 2 leads on the aux light get connected to the 2 pins of the existing connectors, as long as we're talking about conventional aux lighting with halogen bulbs.

would it be cheaper to splice a dinky switch and a relay into the stock foglight switch harness? if so, what kind of relay, switched ground or +?

I'm a bit confused about this one. I thought when you say complete minus the switch, it means all the wiring is complete, from the connector that connects to the switch, through the relay, to battery power, and the 2 connectors to the individual fogs. The connector that connects to the oem fog switch probably have 5 to 6 pins on them, some for the indicator light, some for the actual fog wiring, and some possibly connected to the rest of the headlight wiring (so that the fogs won't turn on with high beams).

A generic switch available at RadioShack is mostly a Single Pole Single Throw type (i.e. 1 button/switch w/ 1 on position), with or without extra pins for switch lighting. If the rest is there, imho, it is much better to stick to oem switch. Afaik, most subaru fog switches should be compatible. I see at least 2 eBay vendor that have sold switches from salvaged Subarus every now and then, you may be able to get one from such vendors for less than US$10 before shipping. Given the plug-and-play benefit, imho it is a reasonable price.