SL/R129: Battery Control Module A2305401045
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2008 mercedes sl550
Battery Control Module A2305401045
I am brand new to this site, and desperately need some help. I have a 2008 Mercedes SL550 convertible. Recently the red battery indicator light came on/off sporadically, then finally came on and stayed on. I took the car to locate Advance Auto, who said battery was fine, but the alternator was only charging at about 12.8 instead of more than 14. I purchased a new aftermarket alternator and belt, took it to my local Mercedes dealer to have them install it. They called and said the battery and alternator was fine, but the battery control Module A2305401045 was bad. Further, they said the part was no longer available, and they offered no solutions. I found one on Ebay for $1500which matched exactly what I need, but the dealer says the BCM is "VIN specific". They said they could only program the used BCM if it was wiped clean, and my used BCM is not wiped clean. Dealer says they have no way to wipe it clean. They recommended I find an online hacker, which sounds shady. I have not returned the used BCM yet. Any suggestions would be very helpful.
FYI, I am not a mechanic, nor do we have any savvy Mercedes/import locations other than the one Mercedes dealership in WV. Right now the car will start and function fine, except the red warning light being constantly on. HELP!
PS. If this is not the correct location for my post, please direct me to it. 2008 hard top convertible SL550
FYI, I am not a mechanic, nor do we have any savvy Mercedes/import locations other than the one Mercedes dealership in WV. Right now the car will start and function fine, except the red warning light being constantly on. HELP!
PS. If this is not the correct location for my post, please direct me to it. 2008 hard top convertible SL550
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Joined: Dec 2005
Posts: 4,057
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From: NJ
2009 SL63 AMG
Few things:
Another video for reference:
Please do not dispose of the original BCM in the car. You have the superseded part number and there is a good chance it can be repaired.
Example of a repair service:
If you truly have no use for the original defective unit, plenty out there would buy it off you for analysis / repair. I'd be happy to as well if you go that route.
There are also some creative aftermarket options emerging for BCM substitutes, but you have several steps you can take before needing to go down that route.
- This is the R129 forum. You have an R230 SL. Correct Forum: https://mbworld.org/forums/sl-class-r230-17/
- The dealership you went to seems misinformed on this subject.
- BCMs in the R230 SLs are not VIN-specific / VIN-locked.
- IF your BCM is defective and you are replacing it with a good working unit, no "online hacking" will be required.
- You don't have to be a professional mechanic to get to the BCM. Being careful with removing trim panels and using basic tools, you can easily access it.
Another video for reference:
Please do not dispose of the original BCM in the car. You have the superseded part number and there is a good chance it can be repaired.
Example of a repair service:
If you truly have no use for the original defective unit, plenty out there would buy it off you for analysis / repair. I'd be happy to as well if you go that route.
There are also some creative aftermarket options emerging for BCM substitutes, but you have several steps you can take before needing to go down that route.
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2008 mercedes sl550
Before I install the used aftermarket BCM I bought from Ebay, I'm going to go ahead and replace the alternator, since I already have a new one ready to be installed. I'm thinking that this could solve the problem, and at least I can rule out the alternator as a problem if I install a new one. What do you think?
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Joined: Dec 2005
Posts: 4,057
Likes: 341
From: NJ
2009 SL63 AMG
Dealerships are rarely knowledgeable about dated platforms. If you're lucky, you'll get an established master tech, but many of those legitimate experts go open their own shops.
Before I install the used aftermarket BCM I bought from Ebay, I'm going to go ahead and replace the alternator, since I already have a new one ready to be installed. I'm thinking that this could solve the problem, and at least I can rule out the alternator as a problem if I install a new one. What do you think?
It's simple to use a readily available tester to get a clean baseline on the health of your batteries and alternator.
There are cheaper / more basic ones, but Foxwell makes a quality product:
To load test the batteries, you need to bring them to a full charge. Any well-rated charger will do, and I'd recommend you disconnect the batteries from the car before charging / testing.
The sequence to disconnect is: Consumer / Rear Battery First, Starter / Front Battery Second. Re-connect sequence is the reverse of that.
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