SL/R230: Battery Control Module A2305401045 Replacement
05-22-2024, 01:23 PM
#26
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Join Date: Feb 2009
Location: CT, USA
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2005 E500, 2004 SL600
Which multipin connector are you talking about? I have a Red Battery Light on Dashboard and can not connect to my BMC and a few other modules on CAN BUS x30/17
05-22-2024, 02:22 PM
#27
Junior Member
05-22-2024, 02:34 PM
#28
Junior Member
Wow this generated a lot of responses!
The other week I got my amp clamp out to see if there was any parasitic load on the starter battery - nothing. I measured the battery voltage for a couple days and it was holding as it should. So it remains a mystery why I had a flat starter battery.
The other week I got my amp clamp out to see if there was any parasitic load on the starter battery - nothing. I measured the battery voltage for a couple days and it was holding as it should. So it remains a mystery why I had a flat starter battery.
05-23-2024, 03:41 AM
#29
Newbie
Thread Starter
05-23-2024, 03:45 AM
#30
Newbie
Thread Starter
When you get the covers in the boot removed at first inspection there are two terminal blocks on the BCM. The one on the left is for the heavy gauge power wires while the one on the right has all the other signal wires. It is a ~14-pin connector that you should be able to gently detach. In the process of disconnecting and reconnecting that 14-pin connector, my BCM problems went away.
05-23-2024, 09:21 AM
#31
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Join Date: Feb 2009
Location: CT, USA
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2005 E500, 2004 SL600
When you get the covers in the boot removed at first inspection there are two terminal blocks on the BCM. The one on the left is for the heavy gauge power wires while the one on the right has all the other signal wires. It is a ~14-pin connector that you should be able to gently detach. In the process of disconnecting and reconnecting that 14-pin connector, my BCM problems went away.
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rjshook (05-23-2024)
05-23-2024, 09:24 AM
#32
Newbie
Thread Starter
There was no obvious corrosion. My thinking was simply that there was just a tiny bit of oxidation and the simple action of disconnecting and reconnecting gave a fresh metal to metal contact.
05-24-2024, 01:02 PM
#33
Senior Member
Guys, yes indeed, this BCM issue has been very well addressed in this forum. Luckily mine still operates good, but my main fear is the fire it could start. For my peace of mind, I covered the BCM with a 3/4" blanket of ceramic fiber just in case it gets ignited.
I have had electronic control boards refurbished by shops in USA and wonder if anyone has had one refurbished.>! I can tell they are not available and the ones in hand of used part dealers, they know the importance of the part as well as the unavailability elsewhere, so they are clamping a good amount of $$$$$ to it. I wonder if any of the "electronic geniuses" in the forum may know how to operate the charging system with no BCM or a similar device.
I am also convinced that some of the issues are created by the corrosive environment inside the trunk due to vapors from the auxiliary battery. If properly vented this will not happen, but in instances some "previous" owners have used an unvented battery which will emit the corrosive vapors inside the truck. In my case the previous owner has an unvented lead acid and it caused one of the microswitch contacts to corrode. If that happens to the thin printed circuit boards inside the BCM, that may be an issue...!
Thinking out loud, the replacement system will be something like the new smart chargers that detect when the battery is fully charged, then switch automatically from high amps to trickle charge...!
I have had electronic control boards refurbished by shops in USA and wonder if anyone has had one refurbished.>! I can tell they are not available and the ones in hand of used part dealers, they know the importance of the part as well as the unavailability elsewhere, so they are clamping a good amount of $$$$$ to it. I wonder if any of the "electronic geniuses" in the forum may know how to operate the charging system with no BCM or a similar device.
I am also convinced that some of the issues are created by the corrosive environment inside the trunk due to vapors from the auxiliary battery. If properly vented this will not happen, but in instances some "previous" owners have used an unvented battery which will emit the corrosive vapors inside the truck. In my case the previous owner has an unvented lead acid and it caused one of the microswitch contacts to corrode. If that happens to the thin printed circuit boards inside the BCM, that may be an issue...!
Thinking out loud, the replacement system will be something like the new smart chargers that detect when the battery is fully charged, then switch automatically from high amps to trickle charge...!
Last edited by elMacko; 05-24-2024 at 01:06 PM. Reason: expanding
05-24-2024, 01:12 PM
#34
Newbie
Thread Starter
Some interesting thoughts. The 'fire blanket' is an interesting idea. However I struggle to think that corrosive vapors are a route cause. The BCM is a well sealed module, when I took the lid off of mine, it was pristine. My car still has a little vent hose in place - when was the vented battery replaced by the sealed battery? The BCM is not only sealed but also under the trunk/boot lining. I really don't see how corrosive vapors are the problem.
If you ignore the diagnostics and control functions, at a most basic level you could replace the BCM with a power diode so that the starter battery is charged by the alternator directly, but cannot be drained by the consumer loads. Saying that, it is most certainly not something I would dream of doing. Remember this is a volume production car, BCM fires are VERY rare. If your BCM conks out, I think you just need to fork over the $$/££/€€ for a replacement from whichever channel has one available.
If you ignore the diagnostics and control functions, at a most basic level you could replace the BCM with a power diode so that the starter battery is charged by the alternator directly, but cannot be drained by the consumer loads. Saying that, it is most certainly not something I would dream of doing. Remember this is a volume production car, BCM fires are VERY rare. If your BCM conks out, I think you just need to fork over the $$/££/€€ for a replacement from whichever channel has one available.
05-24-2024, 02:25 PM
#35
Senior Member
Thank you for the advice my UK friend, I am really against speculative prices....! In the past very often I have used existing subsystems used in other vehicles to retrofit systems that are not readily available or obsolete. In my humble opinion, the BCM is not but a glorified Voltage regulator. I don't see why a common automotive voltage regulator from an old Ford or Chevy couldn't be wired to replace the BCM. All it does is keep the starter battery charge at a certain level, then disconnect! Pretty much what a typical voltage regulator does! I am not messing with that right now, but if ever the moment comes, I will do!
