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help needed - electrical problem - 2009 Impreza


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hi!

I have a base model 2009 Impreza hatchback. 2.5 motor

 

a) if I turn the headlights on, the left (drivers) side come but are faint, high or low beam

 

b) with the headlights Off, the left directional works correctly

 

c) with the headlights ON, the left directional blinks very rapidly but the bulb is very faint

 

d) the hazard lights work fine; all bulbs bright.

 

All things on the Right side work fine.

 

Any idea what my problem might be ? Am guessing the switch on the steering column is bad - not a bad repair and not expensive.

 

thank you

 

john

Edited by jagoulet
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If you have the headlights on and main beam on, what is the effect then?

 

 

I would consider that the low beam grounding wire that goes from the headlight to the stalk is damaged/broken.

 

 

The wiring is a bit quirky on the subies where the power from the battery goes through individual fuses on left and right side and then down to the common input on the headlights. Then there's one separate wire from low and high beam back to the high/low beam switch. However the low beam may be permanently grounded so that it's on also when the high beam is on, so it might be that it's just the grounding wire that's bad on the left headlight.

 

 

Also look here.

453747.png
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If the Low beams are on, the left side is pretty dim, relative to the right.

 

If the High beams are on, the left side is pretty much out entirely.

 

You speak of a ground to the headlight. This is within the harness? The light assembly is all plastic so, unlike old cars, no ground is provided. Where are we physically talking here?

 

thank you!

 

John

 

ps When Subaru powers a light bulb, or anything else, do they do it by grounding it out or by providing 12 V to it?

Edited by jagoulet
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They activate the headlights by grounding them, so it's a wiring harness issue as it looks like.

 

 

There's probably a grounding point somewhere, start to look at the battery area or under the battery pan since that's an area prone to rust/corrosion.

 

 

Can be a rodent issue too.

 

 

Try to read the wiring diagrams on the link I provided above.

453747.png
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I got a multimeter and looked at voltages to all 4 plugs (to headlight elements) in both Hi and Lo beam position, left and right side.

 

Voltages measured from the wiring lead that plugs into the element, to the Neg post on battery.

 

The oddball is the 2 Left side leads to the Outside element in Hi beam mode.

 

Voltage from red lead to ground: 11.54 from black lead to ground 11.1

 

But for comparison, on the Right side in Hi beam mode (which works fine):

 

Voltage from red to ground 11.7 and from black to ground 0.03

 

In Lo beam mode the left and right outside leads all show near identical numbers but if I plug the elements in, the left side is dimmer than the right.

 

Does any of this suggest anything? Have not found any grounds anywhere to be considered. Just the main one from the Neg post to the engine.

 

Weds 11/11: you were right! I scraped a little off one of the black leads (GND) on the left side, ran a temporary jumper to the Neg post on the battery and . . . voila! Everything works fine! So I will solder a permanent lead onto the bare spot and run it to the body and we should be fine.

 

Thanks!

Edited by jagoulet
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