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Hi Bob.It might that you have the same problem as I have with my SL 55 AMG 2002 mod.
The BCM nearly caught fire, and there was a big short circuit in the BCM.
I’m now looking for a new, or rebuild, CAN ANYONE GIVE ME SOM INFO ON WHO, WHERE?
PS, You should disconnect both batteries, find the BCM, and open it, It might look like mine.
I have attached some pictures showing what my BCM look like.
Thank you for your comments. I replaced my BCM with one of the newer designs by Brian Wallace and his partner. No problem since then.
Hi Bob.It might that you have the same problem as I have with my SL 55 AMG 2002 mod.
The BCM nearly caught fire, and there was a big short circuit in the BCM.
I’m now looking for a new, or rebuild, CAN ANYONE GIVE ME SOM INFO ON WHO, WHERE?
PS, You should disconnect both batteries, find the BCM, and open it, It might look like mine.
I have attached some pictures showing what my BCM look like.
As mentioned above, many are replacing their defective BCMs with an aftermarket alternative which performs the basic functions.
They are not available new and used ones on ebay are nearly $2000 with no assurance they even work, and likely won't last long.
Maybe someone can give me some direction. Since I have been working on this car for the last 3 months the red battery warning lamp has been on. I am not sure if it was on when I got the car about a year ago because the car was inoperative.
I replaced the rear/auxiliary/consumer battery about 3 days ago but the warning lamp problem was before that. Just fyi, that battery would not hold a charge. BTW, I have NEVER jump started the car. Just used a quality charger.
I have tested both batteries this morning below are the results.
With car off (and after it set over nightz0:
Front/Starter battery: 12.65 V
Rear/Auxiliary battery: 12.71 V
With car running:
Front/Starter battery: 14.00 V
Rear/Auxiliary: 13.85
The iCarsoft says charging is at 13.79 V but it does not allow to check at each battery so I assume that this the alternator charging voltage.
Any suggestions on where to start looking?
This is with car running.
FYI, the SRS problem will be addressed in a different thread.
Thanks.
Hi. My suggestion to your batteries issues is to take the 2 batteries to an auto parts and ask them to check if the batteries are any good and if they will hold a charge to continue using them. From there you will know and move on to what you think is the best solution for you.
also investigate online and also read your R230 SL500 manual in which order you need to remove both batteries and back on. I just replaced the 2 batteries about a couple of weeks, ago. I also have a 2004 SL500. I remember that prior to installing the 2 new batteries I did try charging them and I was getting the red message just like you. After I installed the batteries I don’t have the red message anymore. I hope this is some help for you.
@Oldmenscar The OP replaced his BCM with the aftermarket solution by Brian Wilson.
However, your suggestion to load test the batteries is a good one. While an auto parts store might have the staff to properly test a battery, good quality auto battery testers are available at low cost. The "Project Farm" YouTube channel just tested over a dozen testers and found that the Ancel brand at $32 worked very well. BTW - these electronic testers measure the internal resistance in the battery which is an accurate indicator of its condition. (The resistance is in the milli-ohm range.)
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