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2006 Outback 2.5i
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Discussion Starter #1
Hi everyone,

My drivers side headlights are dim on low, (car has separate bulbs for high and low beams). When you switch to high-beams, both bulbs on the drivers side go out.

I have had issues in the rear gate in the past as many people on here have had. No radio reception, and also a time when stepping on the brake made the rear wiper come on. Should I start trouble shooting the problem in the rear gate area, or look somewhere else?

All the other lights in the car are working as they should.

Really appreciate any help. It's getting late now, but will probably look into it in the morning...
 

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When the headlight switch is ON and set for the Low beams, are both driver side bulbs lit dimly, or just one?

When the headlight switch is ON and the High beams are selected, are both bulbs on the right side on (bright)?

Start by checking/replacing the headlight fuses -- # 6 and #7 (15 Amps) in the engine compartment fuse box. Also, fuse #19 and #32 (7.5 Amps) in the cabin fuse panel. (The latter fuses are for the headlight relay energizing coils (Left, and Right).

There have been cases of the headlights malfunctioning due to wire problems in the flexible boot to the rear gate, but I believe that affected the headlights equally, not just one side. (Doesn't mean that a fault in that wiring could not be a factor, but look at the fuses first.)
 

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Discussion Starter #3
With the headlights on low beam, both bulbs on the drivers side are on, but dim. When I switch to high beam, both bulbs on the drivers side go out completely.

Also just noticed that when I switch from high beam to low beam, the blue high beam indicator in the instrumentation panel fades out slowly.
 

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With the headlights on low beam, both bulbs on the drivers side are on, but dim. When I switch to high beam, both bulbs on the drivers side go out completely.

Also just noticed that when I switch from high beam to low beam, the blue high beam indicator in the instrumentation panel fades out slowly.
Sure sounds like bad ground for drivers-side bulbs.

On LOW beam, there is no ground-path available so the current is passing thru the OTHER bulb to get to ground... hence they both glow with less intensity.

I could even explain why the blue light on the dash is behaving as you describe... but those facts are not necessary to fix the problem.

Try temporarily jumping bulb-negative to a KNOWN good ground. I bet it will work fine then.

I will send you a bill for my troubleshooting prowess later - LOL
 

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Subaru uses switched grounds to control the headlights. The high and low bulbs are switched separately. There isn't a common ground on each side that would affect both bulbs on one side, but not the bulbs on the other side.

Wiring diagram attached.

Suppose the left side fuse, #7, is blown. When the headlight switch is turned ON, but for low beams, "A H/L-02" is grounded. This grounds the lower side of the low beam bulbs. At this point, on the right side, there's 12 V at connector F59, pin 3, almost none at F59, pin 1, and 12V at F59, pin 2. On the left side, there's no voltage coming in at F58 pin 3 (the fuse is blown).

However, as noted, there is 12 V at F59, pin 3. In addition to the path through the right side low beam bulb to ground there's also continuity through the right side high beam bulb to F59, pin 2 and F58, pin 2, then through the two left side bulbs to F58, pin 1, where it connects to the ground from "A H/L-02". As a result all three bulbs (including the right side high beam bulb) are in series with 12 V across them, and they light up, but not bright. As none of the bulbs is bright, the fact that the right side high beam bulb is glowing might not be noticed because of the brightness of the low beam right next to it.

When the headlight control is switched to high beam, F59, pin 2 and F58, pin 2, are grounded. At this point in addition to the ground for the low beams provided by "A H/L-02", connector F59, pin 1 and F59, pin 2 are grounded (this is through the DAYTIME RUNNING LIGHT CONTROL MODULE high beam grounding circuit at connector B96, pin 3), and as there's no voltage now going to the left side bulbs as there was before -- they are not lit, even dimly.

The slow high beam bulb fade out is probably because there wasn't the right current through the DAYTIME RUNNING LIGHT CONTROL MODULE high beam grounding circuit due to the left side not functioning.
 

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Discussion Starter #6
I went out this morning and I'm scratching my head over this one.

I know a little about wiring issues, but checking the fuses and relays sounded less intimidating to me so I started there. I popped the engine fuse box cover and what do I see? A beautiful, blue, 15 amp fuse lying in the bottom of the tray. I check the label on the inside of the cover for that slot and lo and behold it says l\h h\b.

Not believing this could be it I popped it in. Brilliant white low beams, and my driver side hi beams are working again.

I have no idea how that fuse could have come out, but I will take what I can get on this one. Thanks for all the quick responses. At least I went to bed last night having a plan on how to tackle this.
 

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Subaru uses switched grounds to control the headlights. ....
No problem, then the logic simply reverses and the common-power is the issue. The wiring diagram you supplied bears this out. When BOTH lamps glow... it is obvious the current is flowing thru the other bulb instead of where it belongs.
 
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