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7 Series - E38 (1995 - 2001)

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  #1  
Old 02-25-2013, 02:27 PM
TheRiverSuckout TheRiverSuckout is offline
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Location: St. Louis, MO
 
Join Date: Dec 2012
Posts: 4
Mein Auto: 2001 BMW 740IL
Is it possible I have the wrong battery? Im Having headlight issues

Hello,

Im still having issues with my 2001 BMW 740il. I bought this car from a guy on craigslist about 6 months ago. I didn't seem to have any headlight issues until maybe 1 month into owing it.. but now it's bad. The car doesn't have any issues starting up. It runs fine, and for the first month.. the headlights worked fine too. Then, one night.. while driving on the highway, the headlights went out for about 20 seconds, and the emergency lights or daytime lights came on. Since then, I've not been able to keep the headlights on. Also, when the headlights go out, the brake lights and turn signals do not work either. Sometimes the brake lights are stuck on even when I'm not pressing them. Basically, my external lights are going haywire.. unpredictable and unsafe.. so I cant drive it.

Recently, the battery died because I sat out in the car listening to music while trying to track the problem, and I had it jump started by my Explorer.. The headlights worked for about 10 minutes after the jump. So I started thinking maybe it's something to do with the battery. Well, the batter that is in it was in it when I bought it. It is an Exide HP-31E. I looked this battery up and found it on Amazon.com, and they say it will not fit my car. Can this be the issue? Can the wrong battery cause my external lights to go haywire? Or is it more likely that my LCM is bad? And, is it possible that the wrong battery caused my LCM to go bad?

Please help.. thanks
Bruce
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  #2  
Old 02-25-2013, 04:42 PM
chrisn7 chrisn7 is offline
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Location: Huddersfield, West Yorks
 
Join Date: Oct 2011
Posts: 482
Mein Auto: 750iL
You may have an issue with the Light Control Module, or perhaps the supply to it-there are some 4 fuses. There are certain failsafe features in case of failure of the module, which appears to be happening.

When you say the existing battery will not fit, I presume you mean that it has insufficient capacity? The long wheel case cars have plenty of toys, and need plenty of battery power to drive them (the 750 iL has 2 batteries), so it essential to have a battery that is not only in good condition, but also of correct capacity...Failing batteries are a common cause of unexpected electrical behaviour, due to low voltage, so sort this first...
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  #3  
Old 02-25-2013, 04:55 PM
TheRiverSuckout TheRiverSuckout is offline
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Location: St. Louis, MO
 
Join Date: Dec 2012
Posts: 4
Mein Auto: 2001 BMW 740IL
The battery fits in the car, it doesn't seem to be the wrong shape or size, but Amazon said that this battery would not fit. I've asked a couple mechanic buddies of mine and they said that it shouldn't matter which battery I have as long as it's a 12 volt with enough cold cranking amps. I've also contacted a BMW dealership about it, they say the same thing basically. I've just about ruled out the battery being the issue because the car starts up with no problems every time and has never died on me.

Today, I started it up and the daytime running lights came on as they normally do. I switched the headlights on, but nothing changed. No brake lights, no turn signals, no high beams or brights. The stereo, interior lights, navigation, and all other electronics seem to work fine. I don't want to pay a shop 129$ an hour to do a diagnosis when they say it could be a 2 day job alone.

What would happen if I just bought a used LCM off ebay and swapped it out on my own? I've found a bunch of em on there for $50-$100. I've read that it would need to be coded to my car, but would it fix the issue so I can drive it to a BMW dealership?
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  #4  
Old 02-26-2013, 04:10 PM
chrisn7 chrisn7 is offline
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Location: Huddersfield, West Yorks
 
Join Date: Oct 2011
Posts: 482
Mein Auto: 750iL
Well before you start spending on parts, you really need to know what the problem is..Even if you buy a LCM, you will still incur the cost of having it coded,and BMW dealers are not necessarily to keen to code unknown modules...If you do buy, be sure to get the same part number-some module also have a HW no. and SW no. too. However a later part number as specified in the ETK (electronic parts manual) would be ok too.

(to illustrate, I recently discovered a 5 series General Module in my 750, and this had been the cause of a flat battery/alarm going off when the boot lock was in the thiefproof position)

Since you are satisfied that the Battery is ok, time for diagnostics. It will only take a few minutes to do this and obtain the codes, which will at least point you in the right direection. It might not be the LCM, could be an earth (ground) problem, broken wire, loose plug etc - its tracing things like this that's time consuming.
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  #5  
Old 02-27-2013, 02:03 AM
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BMWFatherFigure BMWFatherFigure is offline
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Location: Perth, Western Australia
 
Join Date: Aug 2012
Posts: 2,144
Mein Auto: E23;E30;E38;E32;E34 +
+1 on simple fault finding. Plugs, fuses, earths, wires all need careful checking for being clean, electrically sound and secure. Has some 'expert' (ie stereo fitter) been into the dash or similar? It seems those guys use Hyundai standards and techniques on BMW exotics - disaster!!
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