#BMW E46 xenon lights flickering

16 messages · Page 1 of 1 (latest)

normal ice
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Hello all,

I have been trying to diagnosis an issue on my friends BMW and I am now truly stumped.

A few weeks ago on a rainy night, both of his xenon headlights started flickering really badly, he had to use his brights in order to drive.

He has since then replaced the ballasts on both sides, replaced the bulbs, and checked all the grounds for any issues, nothing apparently wrong. Headlights are still flickering badly. He gave it to me stumped and I was feeling like the grounds had to be bad somehow because I had this problem on my own BMW E46. I spliced in my own ground at the connector which did nothing. Did it on the other side, nothing. The headlights do not flicker when the engine is off, but when the car is running they flicker, measured 12.1 volts at the connector. I’m totally stumped.

Any advice is helpful, if swapping the xenon’s for LED’s will fix it then I will gladly do so.

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normal ice
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It might also help to know sometime before this all started happening my friend crossed the battery terminals and fucked up a bunch of shit

amber cairn
blazing wave
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Agree with marine. Especially if this started happening at the same time, immediately suspect the portions of the circuit that the headlights have in common.

normal ice
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I’m not terribly keen on replacing that though

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I would like to avoid tamper dot by any means necessary

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The only thing that the circuit goes through is the LCM Module from the battery before it gets to the headlights

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So to me it has to be the LCM somehow

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But it does raise some questions

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Why would it work when the engine is off? Why don’t I see any other symptoms of LCM failure? Any way I could test the LCM?

normal ice
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If the LCM truly was fried in this way there would be other issues accompanying it

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All the other lights would be having this problem

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I’ll do some more testing today to get some better information

blazing wave
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Shot in the dark: pull off your airbox and re-seat your alternator connections. Same with the battery terminals in the trunk, make sure the wiring going into them is secured and not loose, and double check your grounds too.