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2003 Legacy L/SE Wagon (5 Speed)
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Discussion Starter · #1 ·
I have a legacy and a while ago swapped to the separate bulb headlights, but as a result my high's and lows cannot be on at the same time because of the wiring for the original dual filament single bulb set up.

Anyways, I was poking around doing some wiring under the dash and noticed that under the main fuse box there is a slot of 3-4 fuse spots on the bottom right of the fuse box. The labels on the back indicate that one of them is for headlamps, and my car did not have a fuse installed there, I think it called for a 15A fuse. In your outback that came stock with that style headlight, is there a fuse there?

After studying up the wiring diagrams it appears the main difference in the headlight set ups is an additional relay or different behavior of the DRL module. Rather than sticking a random fuse somewhere I wanted to see if anyone has any idea what that does
 

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That block of four fuse slots is referred to as B225. On the 4-light headlight page, at the bottom, there's a diagram of the Relay Block. The four slots are at the left.

The fuse that would be in the block is used with the On Star system. There's wiring diagram pages for On Star and the fuse is shown there, along with an On Star relay that is also in that same relay block.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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Onstar was only available on H6 cars from 2003-2004 (i think).
 

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2003 Legacy L/SE Wagon (5 Speed)
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179 Posts
Discussion Starter · #5 ·
Hmm, I'll take so pictures of it and see if it looks similar to what you have, I guess popping a fuse in couldn't hurt it?

It was more just a question of curiosity, as I've seen lots of Baja/Legacy owners stumped at trying to make them both come on in an upgrade. After putting in HIR highs the low beams are not even needed when the highs are on
 

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2003 Legacy L/SE Wagon (5 Speed)
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179 Posts
Discussion Starter · #6 ·
Here is the fuse labels, they are visible right under the dash next to the ODB connector, I don't see anything for on star. The H/L relay is the one of interest to me
 

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On the cars with OnStar, the relay block (next to the fuse panel) had that additional fuse and a headlight-related relay identified as OnStar Relay-2.

Looking at the wiring diagram for the OnStar system, the purpose of the added fuse and relay appears to be to provide OnStar control of the two headlight relays in the main part of the engine compartment fuse box. In both systems (with or without OnStar) the two headlight relays are switched together. Consequently, if my interpretation of the OnStar components is correct, then it (i.e., the extra fuse and relay) would not affect which bulb (in the 4-bulb system) is lit up because each of the two headlight relays power both the high and low beams (whether 2 or 4 bulb) on their respective sides.
 

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2003 Legacy L/SE Wagon (5 Speed)
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179 Posts
Discussion Starter · #8 ·
Ah that makes sense, I wondered how Subaru integrated those features without a dedicated light control module like other cars I've had. Thanks for the insight
 
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