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Discussion Starter · #1 ·
Hey everyone,

So I was cruising along a few weeks ago when every light from abs to transmission popped up and the car started to drive horribly. Took it to the stealership and they diagnosed it as a bad alternator. I replaced the alternator (not there) with an OEM Bosh and it had the same issue. Then I replaced it again and it had the same issue. There's something draining off power and it's causing the entire car to freak out. The battery has been tested twice and it's fine. We're currently charging it to full to see if that helps.

Any thoughts on the issue?

Thanks
 

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Battery knackered, connections, lead shorting from front to back???

I'm assuming that no one has been fiddling with something they know little about??
 

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Discussion Starter · #3 ·
Hey Robin,

Nope, no fiddling! Only BMW certified mechanics. The battery has tested fine from both the local BMW dealer and Autozone. The lead shorting is a definite possibility, do you have any areas in particular that you'd look at first?

The car was being driven normally at about 8pm at night. I stopped at a stop sign, took a right turn up a slight hill. It was drizzling outside and the vehicle randomly turned on every light including transmission and started to drive weird.
 

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Hey Robin,

Nope, no fiddling! Only BMW certified mechanics. The battery has tested fine from both the local BMW dealer and Autozone. The lead shorting is a definite possibility, do you have any areas in particular that you'd look at first?

The car was being driven normally at about 8pm at night. I stopped at a stop sign, took a right turn up a slight hill. It was drizzling outside and the vehicle randomly turned on every light including transmission and started to drive weird.
Ive seen a flaky junction box cause that. Make sure your junction box doesn't have any signs of moisture
 

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Discussion Starter · #5 ·
Hey Jimmy,

I'll definitely be looking into that, thank you for the suggestion! I went ahead and ordered a new battery (on sale on Amazon for 20% off right now) and that will be my next suspect piece. Thank you so much for the response!
 

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Discussion Starter · #8 ·
Hey Calwaterboy,

Thanks for the reply! I'll definitely keep that in mind, although it is a certified BMW mechanic working on it so I'm sure he knows the ins and outs of that. He's charging the battery full over the weekend and he will then be trying to trace the power draw. We're also looking into the junction box come Monday as suggested by Jimmy. So hopefully we can get it resolved. If you have any other ideas, please post them! Thanks.
 

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Earlier Post: So I was cruising along a few weeks ago when every light from abs to transmission popped up and the car started to drive horribly...

Nope, no fiddling! Only BMW certified mechanics. The battery has tested fine from both the local BMW dealer and Autozone. The lead shorting is a definite possibility, do you have any areas in particular that you'd look at first?

The car was being driven normally at about 8pm at night. I stopped at a stop sign, took a right turn up a slight hill. It was drizzling outside and the vehicle randomly turned on every light including transmission and started to drive weird.
Have you ever noticed a water leak into the front passenger footwell? The Instrument Cluster Module is connected to the JBE (Junction Box Electronic Module) located just behind the glovebox, via the K-Can L & K-Can H Bus connections, at pins 29 & 31 respectively of Connector X14272, which is the 54-pin connector on the Right (there are two alike) on the front of the JBE.

I'd be interested in knowing how the "Certified BMW mechanics" determined that your alternator needed replacing. Did you ever put a voltmeter on the B+ terminal under the hood to test battery voltage with engine running? Should be in range of ~14V.

I would start by opening connectors at the JBE and checking for any water/moisture, cleaning pins with electrical contact cleaner & drying thoroughly with heatgun (low heat). If there are still issues, I would then open the DME case and check for any sign of water in that.

BTW, when you say "vehicle randomly turned on every light" do you mean warning lights on the instrument cluster, or are you talking about other lamps such as interior, etc? Also, has the condition of whatever lights were lit corrected itself since this happened several weeks ago?

George
 

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Discussion Starter · #11 ·
Hey George,

Nope, I've never seen any signs of a water leak in the passenger footwell or driver footwell. The mechanics were a BMW dealership, which diagnosed the alternator and an independent mechanic friend of mine who used to be a tech there. They both arrived at the same conclusion and the new alternator didn't fix it. We're looking into the junction box next and I'll be looking at the one you've stated as well.

By "turned on every light" I mean that when the issue first arose, the traction control, stability, transmission, check engine, brake, and every other warning light turned on on the dash. It did not affect drivability at first and then the next day after driving for about 10 miles the car started to disengage from allowing power to the transmission, OEM nav screen flickered on and off, and wouldn't let me accelerate until the car came back to within 5mph before giving me another few minutes of acceleration.

We're on the third alternator(verified working) and the lights are still on. There's something draining the vehicle's power and we're looking at the junction box on the battery and the one that you've now recommended come Monday. A Very aggravating issue to have!

Thanks for your response!
 

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Discussion Starter · #12 ·
Hey Doug,

Thank you for that! Very helpful and we'll be using that to double check the alternator tomorrow just in case.
 
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