007_e350

Hey Fortlaudsummer, How do we check the BCM ? Any docs ?

konigstiger

Dealer, independent, or anyone with SDS access will need to retrieve stored fault code, check email.

007_e350

Hey thanks Dan - Should I assume the BCM is fine since I haven't gotten the Red Bettery message yet ... Only these;

Low Battery convenince features disabled &
ABS Malfunction &
ESP Malfunction &
the steering wheel becomes hard -

I checked the battery read 12.3 V on the instrument cluster (in the special menu where we get dyno mode)

Alternator charges as follows: (Is this normal ?)
13.4V from 0 to ~20 mph
14.2V from 20 mph onwards

vettdvr

It sounds like the main battery is failing. Alternator is charging if volts go to 14.2 Note however if one of the 3 diode packs fail you will only have 2/3 out put on the alternator and it is possible to have the same issue.

My $$ is still on the main battery. But my wife tells me I am wrong all the time so I might be wrong on this one.

007_e350

But stealership had verified the charging system & closed circuit current leakage (30 mA) - everything was good - Also the Main battery is the new MB battery (less than 2 months old)

Just measured all voltages before starting the car this morning:

- Aux Battery (with one terminal disconnected): 12.6 volts
- Main Battery (with Aux Batt terminal disconnected): 12.48 volts

Here's my concern:
Old Aux battery (Fiamm) lying in the garage also had 12.58 volts
Old Main Battery (MB) also lying in the garage also had 12.4 volts

I also noted: while unlocking the doors SBC pump clicked thrice but didn't buzz brakes lines - I remember it ALWAYS used to buzz upon unlocking ... This has been happening since brakes were bled w/o disconnecting this darn pump

I never had this problem till I bled the darn brakes without disconnecting SBC pump - heeelp guys, maybe the SBC pump is drawing excessing current ? Thats why drains the battery in stop & go traffic ??

vettdvr

I don't believe the sbc is the issue. But 12.58 on the aux is good and the main at 12.4 might be ok. But consider the 12.4 doesn't measure amp reserve only no load voltage. You still might have a issue with the reserve capacity of the installed main battery. You should take the battery and have a carbon pile full load test run on it.

007_e350

Thought I'd check if alternator's charging aux batt, Aux Batt stays at 12.66 even with the car running, is Alternator not charging this one ? Shouldn't it go to 14 v coz of the alternator kickin in

007_e350

Do you know who does this test ?
The current leakage test done by MB showed 30 mA when cars totally shut down - they said its normal
what else could be eating up the battery ? & I know my problem starts when I sit on the brake for long & bleeding did something to either the relay or God know what..

vettdvr

Autozone in my neighborhood had this test equipment. It basically test the reserve capacity of the battery. I have a gell cell batterry in my corvette that is 6 yrs old and cranking slow. It only has 11.2 volts engine off. However everytime I hit the key it starts. After driving for 85 miles I took it to AZ for the test. They told me my battery needed recharging,, which basically meant it did not have full capacity. So now I know it needs replacing. I suspect you have a similar issue with your main battery.

007_e350

Thats what stealership said too & they charged the Main battery but the darn thing became weak again so I went ahead and replaced it twice already -- how can all batteries become weak after 2 weeks ? Is there an electrical component thats messing up the battery ? (The closed loop current leakage was fine with the car shut off - but what about when car's running ? why isn't the Alternator taking care of that ?)

vettdvr

Are the batteries you buying AGM meeting OEM specs.

If the dealer isn't putting in the correct battery you will have this problem.

Verify the battery part number at the parts counter if necessary to confirm you have the correct battery. Others have bought new batteries that "fit" and have the same issues you have. New doesn't mean,, correct,, meet specs, or old battery never used on the shelf.

007_e350

Yeah this one is identical to the original one I took out - I'll post the part no. on it a little later -- Also, he told me this battery came in that morning & wasn't like sitting on the bench..

Interesting to find out my old MB battery still had 12.48 volts..

vettdvr

Remember I did cover in previous post that is 1 of 3 diode packs are failing in the alternator/regulator you won't be able to keep your battery fully charged and that it will give you a low voltage warning with lots of equipment on.

007_e350

Ok, but if alternator's diode fails (any one of the 3) then I shouldn't see 14.2 volts either right ?

vettdvr

Volts and amps are two different things.

It is possible to have 14.2 volts with a diode pack bad. However if your alternator is a 90 amp and 1 diode pack is bad it will only be putting out 60 amps which means it will take longer to charge the battery. On short trips this won't be enough to keep the battery charged but on longer drives it might be able to keep up.

007_e350

ok, Should I plug in the Amp meter between battery's -ve and BCM and crank the car to see how many amps are being pumped into the battery ?

Also, I remember when I was putting in the driver side parking lamp (4 months ago), the housing wont go into the headlamp & I believe I turned it a little too much (maybe 3 full circles or so) ... the battery issue started after that over months ... is there a way to check any shortage in that line ?

vettdvr

Amp meters used to measure full load must be rated for that load. If your system has a 100 amp charging system then the amp meter must be rated for that amount. Anything less could be instant burnout failure/fire. A 100+ ampmeter with proper shunt is a big piece of test equipment.

The proper way would be to use testing equipment that will actually measure and look for the 3 individual pulses from the alternator to confirm it is working. What this means is you should take it somewhere with the proper test equipment to verify the alternator. If your battery is in a low state of charge for this test it will draw high amps from the alternator and indicate low voltage. This is a precision test. If you find noone who can do this test I would recommend a good dealer. If you aren't having success with your current dealer you will have to find another.

For the light you had an issue with. I do not have enough information to answer that question without more information. However consider the light is off with the car off therefore no power. Shorts normally blow fuses or trip breakers/fuseable links. If you have none of these and the light works normally it is 'probably' not a problem.

007_e350

oh boy u're right -- 100Amps could probably toast me alive.. I dont understand why MB dealership would declare charging system in working condition...

vettdvr

Are you in warranty? UMMM

Might consider another dealership. Remember you still have a problem you brought to MB and it hasn't been resolved. You might see your local dealer and ask for MB direct help.

inrealtime

Thanks to this thread I was able to save money bypassing the dealership. Bought the Diehard 14-BS & with the install guide from vettdrv Main battery was at 12.6v, but the Aux was at 10.6v. Bought the Diehard 14-BS & with the install from vettdrv all went well. No errors messages when done.

Thanks

007_e350

hey vettdvr,
I swapped out the alternator too last night - The Red Battery/Alternator msg is gone but at night I get low voltage alongwith ESP & ABS malfunction warning... When I rev it, it goes away too ... My old battery read 12.6 in the garage tonight, so battery wasn;t the issue ?? Why is the new battery also showing low battery after a month ?

Nait Sirhc

Just swapped the aux battery out in the garage. The battery had built-in metal terminals with bolt holes, and the cable ends (which are made to fit over a square edge, but the edge on my battery terminal was too far) fit after a bit of adjustment (had to bolt them on facing vertical instead of horizontal).

Wound up keeping power to it by running jumper cables from my girlfriend's Passat, to little 18-gauge alligator clips, and then clipping those to the lowest point I could find on the AMG's battery cables.

Worked like a charm!

vettdvr

Did you also swap the regulator as part of the alternator. At 12.6 volts your battery should be at full charge. Given you have the correct gell cell main battery, your aux battery is also in the 12.6 range, alternator is working with new regulator. If you still have an issue we have missed something and you will need dealer support.

Verify your aux battery voltage again engine off to make sure it is fully charged.

007_e350

I swapped out the entire alternator w/ built in regulator..

Last night I noticed 2 things:

1- With only park lamps on: when I increase the RPM to 3k, they're ok - but when the RPM drops from 3k to 600 I see flickering - tried this a couple of times saw it everytime...

2- With the car shutoff and even with alrm system armed, no accessory works except the command sys .... I hit seat adjusters they dont work but Radio, CD still works -- could this be a mafunction ?

fortlaudsummer

You probably just have to normalize some components (seats, windows, sunroof, steering, etc.). Instructions are in the manual