Weird headlight issue... So strange...

[BobombETA]

I have a lowbeam out.

Except when I flip on my highbeams all four lights come on, including the lowbeam that normally doesn't work.

I'm really lost on this one. If it's any help, all of my dash lights flicker when I turn on my headlights. The one lowbeam that works also flickers.

Why does the lowbeam get power only when the highbeams are switched on?

Again this is only a problem with one light, the other lowbeam comes on when the switch is pulled.

[slow e30]

sounds like a short of some sort. check your wiring and make sure your fuses and relays are good and tight.

[BobombETA]

Wouldn't a short mean that power wouldn't reach it regardless of me flipping the high beam switch?

[John in VA]

If your using the USA-issued sealed beams, the outer/low beams have both a low and high filament in them. Perhaps the low filament in that one has burned out. You could swap the outer lights side to side and see if the problem moves to the other side.

[theox69]

What year's your car?
I read somewhere in the Bentley that e30's of a certain year had lowbeam fuse issues...

[BobombETA]

If your using the USA-issued sealed beams, the outer/low beams have both a low and high filament in them. Perhaps the low filament in that one has burned out. You could swap the outer lights side to side and see if the problem moves to the other side.

I should have mentioned that I already tried this.

What year's your car?
I read somewhere in the Bentley that e30's of a certain year had lowbeam fuse issues...

1984

[MR 325]

Install ellipsoids, problem solved. :)

[rThor432]

Wish I could copy/paste or link to the wiring diagram on BMW's site, that would make this much easier..

Check fuses 13 and 14, which supply power to the low beam function of the dual filament bulbs. These fuses are the only thing between the headlamp relay and the bulbs, so if one is working, the other isnt, and low beams work the problem should be there. The ground is shared at the headlight, like the power supply for the high beams, so that should be fine if the high beams are working.

If neither are blown, try putting direct power to the pin on the headlight connector for the low beam bulb. Should be the Yellow/White wire for the drivers side or the Yellow/Blue. I'm assuming blue, for some reason the diagram says "YL/BU", should be "GE/BL" for Yellow/Blue, but they did something funny with this diagram..

I'm tired, so I hope this makes some sense and helps a bit.

[BobombETA]

Install ellipsoids, problem solved. :)

Could this really fix it? I already bought the pigtails off of you...

[MR 325]

Could this really fix it? I already bought the pigtails off of you...

I really don't know. I had nothing informative to add so I added that. :)

[BobombETA]

Boo.

[dgdavidson]

Why does the lowbeam get power only when the highbeams are switched on?

ETM page 6312-1 shows that one of the bulbs is a dual high/low beam bulb. I'm guessing that you have no power to the low beam filament of the bad bulb and that what you're seeing is the high beam filament.

So like rThor said, check fuses 13 and 14 and then the wire between the fuse and the light bulb.