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MY08 cabrio MY09 Brabus MY21 Bolt
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Discussion Starter · #1 ·
Garage Queen 09 Brabus with 15,700 miles had become “possessed” emitting random droning noises from the subwoofer. Upon starting, turning off, radio on & off.

Had plans to replace the subwoofer but ironically thought that I’d change the 2012 (9 year old) 12V (flooded) battery first. Swapped out the old replacing it with a 12V AGM.

After driving for a day or two I was shocked to find that all droning had stopped!

While I find it hard to believe, seems that this is yet another smart malady that just might go away with a NEW BATTERY…
 

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Glad you got it solved. May have been crying out "you're gonna blow my alternator if you don't change the 12 V soon".

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MY08 cabrio MY09 Brabus MY21 Bolt
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Discussion Starter · #4 ·
Did you find any battery cable corrosion while replacing Battery?
No corrosion on The Garage Queen cables but a little rust in the bottom of the battery well thanks to prior owners misalignment of the A/C drain tube

Did add a pigtail (above foam/beneath carpet) to facilitate easier access to check the battery (+ battery post/- frame) condition for testing/charging.

Contemplating extending the wire through the firewall for bonnet access?
32C880F1-EAA4-4A57-B70B-0E82115F9ED2.jpeg
 

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Someone on here definitely ran the pigtail through the firewall all the way to the front where the service flap releases are. (I wish I remember who: was it @Yinzer?). I ran the short one that came with the charger to the right of the passenger foot well, right next to the door. It BARELY reached, but stuck out just enough for my tiny-ish fingers to be able to grasp it. (Wish I took a pic but didn't).

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I think the cable extender was JWIGHT. I have Del Tran battery tenders. They offer an extended length cable (15 feet, if I remember correctly) for about 10 dollars several years ago.
 

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MY08 cabrio MY09 Brabus MY21 Bolt
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Discussion Starter · #7 ·
UPDATE - so, NOT a complete success?

Have been able to drive entire days with the random noise (radio on/off) silenced EXCEPT on initial start up after overnight rest?

Again, only change was a new AGM 12V.

Likely points to voltage issue, perhaps a capacitor in the under seat sub???
 

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A capacitor's job is to provide a steady voltage/current to a device. Switch/Relay perhaps?

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There are such things as line filter capacitors. Wouldn’t know if one is found there but maybe it should be.
 

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Or you could just unplug it, like quite a few others have done. I ended up plugging mine back in because I had gotten a new battery beginning of the year, it kept making the noise when I would start or shut the car off so I just unplugged it again.
From what I understand it's a pretty poor subwoofer.
Like miss Mercedes says, cheapest product from the cheapest bid contract.
 
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