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2007 2.5X 5mt
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Discussion Starter #1
Installed some auxillary Fog lights. I am wiring them so the relay coil gets engergized when the factory fog lights are on. Becuase of the low side switching in these cars I am unsure which wire to tap. I am afraid if i tap the wrong part of the fog circuit the aux fog lights will stay on unless manually switched.
 

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2018 2.5i Premium CVT
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Fogs are switched on the high side, both the lights themselves and the relay that sends power to them. Check the diagram and description at this post for more information. I think that terminal 3 on the switch would be your best bet. Or you could tap off of the wire that feeds the bulb itself.

This assumes that your Forester is wired the same as mine.


Help us help you by filling out the vital details of your Forester in your signature. Year, model, transmission type ought to do it just fine. That way we can fine tune any advice on this and other questions you might ask.

Standard disclaimer: There could be differences among models, model years, transmission or engine types, national markets, or even within a model year. Remember, this is an international forum. Exterior lights and any device that employs the radio spectrum may be subject to differences due to national or even local regulations. Subaru's official wiring diagrams have occasionally been found to be incorrect. Test everything before proceeding. Follow these instructions at your own risk. May contain peanuts. YMMV!

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2007 2.5X 5mt
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Discussion Starter #3 (Edited)
Ok you were right, The fogs are switch on the high side. Confirmed this with my multi-meter. Tapped left hand fog light wire (white) going to bulb. Got everything soldered in place all works good.

Just got to do some "finishing work" like putting all my wiring in plastic conduit and wrapping in electrical tape to give it a stock look. I hate the look of exposed wires running to and fro in the engine bay.
 

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2007 2.5X 5mt
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Discussion Starter #4
bbottomley, I need your help once again!

I need to splice in a normally closed relay into the headlamp circuit to kill the headlamps when the fogs are switch on. Here is my schematic on what I have done/am doing.

 

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Super Moderator
2018 2.5i Premium CVT
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You want the headlights totally off when the fogs are on? That doesn't strike me as very safe.

I fear that it's going to be a bit more complicated than what you've drawn. There might be some sort of loop here. A chicken and egg contention. The stock fogs only come on with low beams, but the low beams won't come on because the fogs are on. So the fogs won't come on ... .

I've never investigated one aspect of the setup, but Ferret tells me that there's also a path through the high beam filaments that's associated with a fog light relay. DRLs could further confuse things. It's all mixed together in there.

I'm thinking that it might be easier to do radical surgery. Bypass all the stock stuff. It's pretty flimsy anyway. We lose over 2 volts in the wiring and switching of the high beams.

Confirm that you really want all headlights off when fogs are on.
 

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2007 2.5X 5mt
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Discussion Starter #6 (Edited)
I got the factory fog relay coil re-wired so the coil is energized by the park lamp circuit (simple mod done behind fuse box). So the High and Low beam aren't a factor (see pic). I wanted the headlights off with the fog becuase the headlamps reflect alot of light back so using them with the aux fogs seems counter-productive to me. Also the same reason I disconnected the DRL as of now (I ALWAYS keep the headlamps in the on position anyway since they turn off with the key, I have had them on since the day I bought the car, so I don't even use the DLR anyway) Plus running the headlamps, Fac fogs and aux fogs seems like a bit too much amp draw for my liking.


(DLR disabled and headlamp switch in "park" position"
 

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Well then, it looks like you're good to go! Just cross your fingers that you don't encounter a sharp-eyed cop coming in the other direction who needs to write out a few more tickets to get up to his quota for the month.
 
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