Wiring help needed w/ rear fog mod...

[prelude/2.5rs]

Well...I finally found an easy solution for a rear fog light on my 02/03 WRX wagon. Long story short, I'm eliminating the reverse light on the driver side. I guess this is the proper way to mod USDM to house rear fogs when you go overseas. I plan on using a switch and relay to operate it. My question is: when running a (+) wire from the relay to the battery, what amp in-line fuse should I use? Or, is there a safer way to get 12V? I'm using a 12V relay and the rear fog consists of LED's that operate off of 12V. Also, I'm using a 5 prong 12V Bosch relay, but am only using 4 prongs. They are listed as #'s 86, 85, 87, and 30 (87a is the center one which I am not using). Here's a rough diagram on how they're positioned:

86
30 87a 87
85

Correct me if I'm wrong, but I plan on running the power into prong 87, ground prong 85, a wire from prong 30 will go to the rear fog (+), and prong 86 will be the switch. My question is: where do I run the other end of the switch to if only one side is to the relay? I'm guessing to just ground it, but I need you guys to confirm Let me know what you guys think. Any suggestions or corrections are appreciated. Thanks!

Mike

Here's a couple of pics:

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[prelude/2.5rs]

anyone...

[pityr]

might this help alittle?

Sounds like you have it right.

[Handsdown]

makes sense to me. awesome schematic.

[prelude/2.5rs]

Thanks for the diagram. It looks like I have the relay set up right. My only questions left are: 1) Should I run the power for the relay right from the battery? 2) If so, what size in-line fuse should I use? 3) The positive end of the switch I'm using goes to the 86 prong, but where does the other end of the switch go? Do I just ground it? Thanks for the help so far. Keep the info coming.

Mike

[Psydotek]

Ok, switch goes to 86. You'll need to tap the switch to a power source somewhere, most easily done by using a fuse tap (found at most any auto parts store) and tapping to the radio fuse behind the little coin box under the foglamp and cruise control switch. This will let you draw power to activate the relay and by having it hooked to the radio fuse, the lights will not come on unless you have the key in the ignition.

Ground goes to 85 (this is to complete the circuit for the switch)

Power from battery goes into 30.

87 will go to whatever device you want to power.

Put your fuse between the battery and prong 30. You'll want a fuse that's just above whatever amps your lamps will be drawing. I'm not sure what wattage the bulbs are, but use this equation: total wattage of devices/voltage=amps drawn. For example, my auxiliary lamps use pairs of 55w bulbs. So since our cars have a 12 volt system, using the equation it would be (55*2)/12=9.17, therefore i'd use a 10 amp fuse. I think the reverse lights use a much lower wattage bulb so you'll be able to use a smaller fuse. Search around for the wattage.

The only problem i forsee is that the relay is an "either or" switch, it'll be either 87 or 87a which is useful for selecting between two different devices. If you're feeling really gutsy you can use the relay to switch between using the reverse lights as reverse lights or rear foglights. But if you want a simple "on/off" switch, you should just pick up another relay with a single 87 pin. They're not too expensive. I have a bunch of extra Hella relays with a single 87 pin laying around here if you want one (they're from all the light kits i've bought, i just never used the wiring harness that was included).

[prelude/2.5rs]

Originally Posted by Psydotek

Ok, switch goes to 86. You'll need to tap the switch to a power source somewhere, most easily done by using a fuse tap (found at most any auto parts store) and tapping to the radio fuse behind the little coin box under the foglamp and cruise control switch. This will let you draw power to activate the relay and by having it hooked to the radio fuse, the lights will not come on unless you have the key in the ignition.

So you're saying, one end of the switch comes from a 12V source(somewhere in dash) and the other end of the switch goes to the relay(pin 86). It makes sense now. Thanks for the offer on the relay, but I think I have a few 4-prong relays in the basement. Now as far as the whole in-line fuse goes...I'm not sure what wattage these LED's run at. I know they just run off of 12V. I'm going to try a 10 AMP fuse and see how it goes. Thanks for the help, Psydotek. Keep the info coming, guys!

Mike

[prelude/2.5rs]

^^^^^