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2015 Forester 2.5 Manual
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Hey guy, long time reader first time poster. So much good info on here! I have a 2015 forester 2.5 m/t. I got all the parts to do the OEM fog light install. All wires are there from the factory, plugged lights in, switch in, relay in. Really simple except when i push the button ... NO LIGHTS! I cant hear the relay click when i push the button. Button lights up when i turn the headlight switch to the marker light setting. I bench tested the bulbs and they are good. Has anyone run into this issue? Am i missing something? Any help is greatly appreciated.
 

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G'day & Welcome NBM

Not sure what's wrong - is there a proper earth and a tip that Subies are negative switched in case that helps.
 

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2016 & 2018 2.5i Premium CVT
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'Illumination' light in the switch is independent of foglight circuitry. Do you see the brighter ON light in your tests?

Foglights only work when headlights are on and in low beam. Have you tested in that condition?

You didn't mention fuse. What does owners manual say about that?
 

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2016 & 2018 2.5i Premium CVT
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I'm sure. But one can always get tripped up by a 'Subaru thing'.
 

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2016 & 2018 2.5i Premium CVT
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Per wiring diagram, it's powered from Fuse 29 in the footwell fuse block. Switched on positive side by relay. Relay triggered from BIU, the internal logic of which is of course incomprehensible.

Diagram attached.
 

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The 2019 Owner's Manual does seem to say the fogs can be activated when the headlights are on rather than just the parking lights - which I find very odd as you may not want your headlights on in heavy fog.
 

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2011 Forester 2.5X Automatic
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Any chance there's a fuse for this circuit that, since it wasn't installed at the factory, isn't there?

The lamp circuit probably uses a control circuit to power the relay. While all you have to deal with is 12vdc this control circuit draws lots less current and therefore doesn't require some super heavy duty switch to turn the lamps on. That heavy duty switch is the relay. A low amp circuit is used to energize the relay (essentially a heavy duty switch) and the high current is passed through the relay to from the high amperage fuse box in the engine compartment which is usually connected directly to the battery.

Check for a missing fuse in the under dash fuse panel.
 

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If fuse 29 is dedicated to fogs, and I would expect that it would be due to the wattage of the bulbs, then it most probably wouldn't be installed if the car wasn't equipped with fogs.

The relay is controlled by the BIU, Body Integrated Unit, a multi-purpose module that controls most everything.

As for requiring low beams (and only low beams), it has been that way since my 2003, and probably forever. In the US anyway. In some places it's a legal requirement.
 
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