anc4

03 sl500 w/ 54k miles, car wasn't used for the last 4 weeks, battery needed to be recharged, the car doesn't recognize the keyless go, i have to insert the key in the ignition, then it recognizes the keyless go. 10 seconds after turning off the ignition, either by keyless or keyed, the car appears as if the battery is disconnected
anyone have a similar situation?
thanx,
also, the ring on the abc tandem pump pulley has separated from the pulley, can it be re welded? is it necessary ( i imagine it is, why would it be there)?

kbob999

You probably need a new battery in the back. This fixes 99% of these electrical problems.

As for the tandem pump...I've seen a DIY to replace the pulleys. Might be the best option. Anything broken probably needs to be fixed.

anc4

Ur correct, had roadside per place the rear battery that they replaced in January and most things r good. The red battery warning light is still on , will that reset itself or do I need MLB to do that?
Regarding the pulley have u seen posts on repairing or replacing the pulley and what damage can be done if I drive the car w/ the pulley ringless?
Thanx

anc4

had the consumer battery replaced, working well but the red battery visit workshop light still on,
this am, the consumer battery reads 5.1 volt and won't take a charge, start the car and now the rear battery is showing 11.5 and is taking a charge!! very confused, any help is greatly appreciated

cyglee

Your consumer battery is not being charged. The starter battery and consumer battery should be receiving 14.+ volts from the alternator. I recently replaced my voltage regulator to correct a similar charging issue. My guess is that the worn brushes on the voltage regulator diminished the alternator output, and so the battery control module kept the starter battery charging, at the expense of the consumer battery. Hope this helps!

bobterry99

This suggests a problem with the starter battery. According to M-B, the fault must be cleared using Star Diagnosis. That said, I had this fault, and I don't recall using Star Diagnosis to clear it.

The "consumer" battery is the rear battery, so this statement is confusing to me.

anc4

1st thing in the morning, the rear (consumer) battery reads 5.1 volts and won't take a charge. once i start the car, the rear consumer battery now reads 13.9 (with car running) if i turn off the car, the rear battery reads 11.9. if i wait the rear (consumer) battery goes back to 5.1 and won't take a charge. i've never seen anything like this before. trying to access the fuses under the subwoofer but am having trouble getting the sub out.
thanx

cyglee

How old is the starter battery, and what is that charging voltage (with car running)?

anc4

not sure of the age and couldn't locate the mm/yyyy sticker and 13.4 volts

cyglee

If the starter battery is much more than 4 years old, I would consider replacing it. I'm thinking your voltage regulator is limiting your alternator output, and the battery control module may be compensating for a weak starter battery, and not sending a sufficient charging voltage to the consumer battery. As for the passenger foot well fuses, if you did not cause a surge by jumping the batteries, I would save all that effort for now. The VR is not that difficult nor pricey to replace. Good luck!

anc4

but why does the consumer battery seem to be disconnected (in the morning) until i start the car and now it's connected?
i have used both a ctek and an external battery charger on both the batteries, could this have done any damage,
thanx again for your help

cyglee

I am leery of using any external chargers (other than ctek type) unless the batteries are disconnected from the car. Also, the consumer battery is AGM, so use the snowflake setting on the ctek. And, the order of disconnecting batteries is the consumer first, then starter. Reconnecting is starter first, then consumer. I am no expert, but learning from others' posts and experiences. I also looked at the battery control module, checking connections, and replacing a relay since I had the trunk interior opened up.

anc4

i use a charger that is for agm batteries. my ctek isn't adjustable but has recently started making strange sounds. i have disconnected the consumer battery and am charging it to see if it retains the charge overnight. once i reconnect it, based on your previous message, should i disconnect and reconnect the starter battery before i reconnect the consumer or is that just if i disconnect them both?
you mentioned the bcm and relay in the trunk, can you enlighten me as to where they are and how i would test them?
thanx for all your help my garage queen and i greatly appreciate it.
ps when i started the car after 1 month of non use, a rat crawled out of the engine compartment, i haven't found any evidence of it being there (was near the starter battery)

Rudeney

Here the rule: Only connect or disconnect the starter battery when the consumer battery is disconnected.

cyglee

Geez! The rat has good taste! Check all the wires in the general area for any damage. No, if disconnecting consumer battery only, just reconnect it. You will have to reset your windows, just open all the way down, and all way up. Hopefully it will take a full charge, reconnect and check again for charging voltage at starter and consumer battery. I'm thinking I would also take out the starter battery, charge externally, look for date sticker, and explore rat damage. There is a electrical system document floating around. Try searching for battery control module. And, do you have an SDS?

anc4

update - i disconnected the consumer battery and charged it, took voltage readings at 9 pm and 9 am and it was 11.9 and 11.8 respectively. then connected the consumer battery but did not reconnect the ctek. consumer battery is at 11.8 volts (not running the engine) and has held for approx 36 hours. i'll buy a new ctek and see if the original one (13 yrs old w/ the mb logo) has failed and is creating issues.
great forum and thanx for everyone's help
ps do you think i should reconnect the original ctek and see what happens?

cyglee

Here's a link to the source document that answered many questions:
http://www.benzworld.org/forums/atta...battery-system


The question is why your new consumer battery is not charging in the car. Is the red battery icon still present? If your starter battery is giving low voltage signals, or insufficient charging issues, the bcm will cause charging issues to the consumer battery. Check again the voltage of both batteries, not running and running. And consider load testing the starter battery at a local autoparts store if the age of battery is questionable.

anc4

the consumer battery and the starter battery are charging, and w/o the ctek the consumer battery doesn't turn off at night. as of now, kiss of death right?, the charging system is working properly. do you think the ctek could have an issue?

kbob999

It must be a plague...now my car has the red battery icon!
SDS shows no faults; checked fuses under subwoofer (what a pain) both OK; rear battery is only a year old and takes charge; front is 4.5 years old and may be on the way out.

The big clue is that the rear battery voltage does not go up when the car is running, which means my alternator or regulator is not putting out voltage. I replaced the alternator 2000 miles ago, so I didn't suspect it would die so fast. I'll check voltages to the alternator next. It needs power to make power.

I'll keep you guys posted on the cure.

anc4

so i drive the car yesterday and all is wonderful. i go to start the car this am and the consumer battery is at 5.1 volts. the starter is at 12.3 and easily starts the car. once i start the car the voltage at the consumer is 13.7. something is turning the circuit off to the consumer battery? i connected an external battery charger to the consumer and a minute later i hear a click and the charger is now not charging the consumer battery! if i start the car then the rear battery will take a charge, both from the alternator and from the external charger. i hate electrical issues.

next2pool

A fully charged battery should read 12.6 V sitting after idle an hour or so after a full charge. 12.2 V is considered a fully discharged battery. It looks like your trunk battery is not able to hold a sufficient charge. Your readings indicate that your alternator is OK and trying to bring it up to 13 + volts. If your charger kicks off, it indicates a shorted battery. It looks to me like you need a new convenience battery.

anc4

thank you!
just pulled both batteries, the starter is dated 9/11 and if it holds only 12 volts it needs to be replaced,
the consumer battery was just installed by mb roadside 2 weeks ago, i'm charging the consumer directly and it kicked off after 30 seconds, i then disconnected the charger, attached it to another battery to make sure the charger was working properly, it did, then connected again to the consumer and it's now charging,
thanks again

anc4

starter battery is showing 12.2 out of the car,

cyglee

Ok, time to change that starter battery. Low voltage signals from an aging starter battery initiates electrical gremlins. I surmise (experts can correct me) that the battery control module shifts the charging system to the starter battery, so to keep from being stranded, at the expense of the consumer battery. As for your fairly new consumer battery, significantly discharging an AGM battery can ruin it. You may consider a warranty replacement, or at least have it load tested.

cyglee

And, back to the alternator and/or voltage regulator... I considered the charging system output was not producing enough to charge both batteries, so changing the VR boosted my alternator output to 14.+volts at both batteries. For good measure, I replaced the K57 relay (inexpensive part) when pulling back the right side trunk liner to check connections of the battery control module.