Celicasaur

You mean that it's not got enough juice left in it to hold a charge? I'd buy that solution, but I must ask why is the small battery now not showing 14v (or anything other than 12.6) when the engine is running....?

vettdvr

Engine running is reading alternator output.

Engine off reads battery

Celicasaur

Absolutely. But I mean, why is the main battery showing the alternator output then and why is the small battery not showing any movement, despite a 'fine' aux battery relay? Is there another common relay which could cause this behaviour?

spinn

sorry, I'm late to the program...can the battery voltage of the aux battery be read through FSS? i thought that was just for the main battery.

Celicasaur

FSS?

I have been measuring with a little multimeter

spinn

OK, just making sure as all the talk sounded like it was readily available like the main battery. I was having trouble with my multimeter, so I never got a proper read yet.

Celicasaur

I just connected a healthy battery to the aux battery relay and then put my voltmeter in the ohm setting (200) and got a reading of 035 (or was is 35...I can't remember, but 35 was definitely there) - can anybody tell me if that means the relay is fine?

I gave the contacts a quick once over with a rotary wire brush, put it back in the car, but the damn aux battery wont show any increase in voltage once the car is jumpstarted.

Hmmm....the hunt continues...

Celicasaur

Anybody...?

vettdvr

Have you ever pulled the main battery and had it fully load tested?

Celicasaur

No.....not sure what that is, but I have an idea.

I'll google what that means

Celicasaur

ok i performed a quick test this morning.

with the battery still disconnected from the other day of charging it via a jump start, it showed ~11.5v. As soon as the battery was connected, the voltage dropped fairly quickly to ~4.5v within 2 minutes of watching it.

I took the battery out the car and gave it one final check but the voltage was then showing ~10.x volts arrrgggghhhhhh, how confusing!!

I've dropped it off now to the local spares shop to test and see if there is a fault with the battery.

Celicasaur

ok so the guy said there's nothing wrong with the battery and all it needed was a full charge. i took hit home and checked the voltage beforehand which said 12.0.1 volts...i was like...hmmm...this should be at least 12.2 at the bare minimum.

I checked the contacts with the battery connected and i wasn't seeing that horrid rapid drain that i saw this morning. car started first time. main battery showing 13.8, aux 12.75. with car off after 15 minutes idling, main shows 12.6 and aux 12.6.

FML it was the battery all along....thanks guys

vettdvr

Why did the battery need a full charge? Is the charging system working or is there internal shortage in the main battery? You still have a problem but time will tell.

Celicasaur

I really don't know man. I went to the car today and it unlocked/started with no problems. Charging system...it appears to be working I guess, but what I might do soon it change the alternator brush packs just to be on the safe side. The last thing I want to get stuck somewhere in the cold winter.

I agree with you though, the problem must still be lingering, waiting to rear it's ugly head, but I guess when it does, I'll get the battery changed under warranty or something.

Green E-300 DT

Just the same as my aux. battery was when I replaced it.

I will bet that your aux battery is the original and therefore seven or more years old? There is a date on that Italian made battery.

That was all that was wrong with mine and that is what would cause the red battery warning
to come on every morning. After starting the car and then shutting it off after a minute
and then restating it, the red warning would disappear and stay off all day.
It turned out that my original aux. battery had one dead cell.

HTHs



DHG

Celicasaur

Hmmm yeah looks like I might need to budget a couple hundred bux to change the battery and alternator brush pack before the cold winter sets in, to ensure reliability. Buying a new aux battery is nowhere near as bad as buying a new main battery I guess

Celicasaur

No, headlights are fine for me

Although annoying with all the on/off battery issues, my command system has issues and the car is acting as though the ignition is off, so I can't set the time, open the cd changer, adjust volume on the 'wheel etc. It's happened before and normally it was a case of just disconnecting the battery again and trying, but it's not doing it this time. I'm sure it'll come back on though (hopefully!) it normally does.

HUDS_E500

(Im new so bear with me, And hello everyone)
But heres a good one.. Just bought a 2003 E500 from a local reputable large dealership near me (Nissan, Toyota, VW not MB) They changed the main battery,(Red battery warning light on) I told them there was another battery under the airbox under the hood (it appeared they didnt know, yes very scary) they changed that as well, even though they said it wasnt bad. Still didnt fix the issue, Light is still on. The alternator is charging as it should.. Also another issue, they changed all brake pads and sensors but there is a brake malfunction light on too.. Im lost on what to do.. They said there was no codes? Seems like if a malfunction light is on there should be a code, Im not a mechanic, but maybe im wrong. Luckily theyre fixing it for me no cost. They`ve had it in the shop for about 5-6 hours today messing with it. I think theyre going to refer to someone (not in their garage) with more expertise. So maybe if i can come up with something it may save me the time of having them strip it to the bumpers or flying it back to germany for diagnosis.. Not having much faith in these guys.. Just want my car back.. Any ideas guys?

spinn

You said it right there...don't take it back to those guys. Take it to a reputable Mercedes repair shop.

Diesel Benz

You are right, if the cluster shows the red warning, there would be a fault code that Star diagnosis could read (it does not work the other way around, not all diagnosis fault codes trigger fault indicators at the cluster). Perhaps the shop was using a generic code reader.

If you read this thread, I think you can find out that at least the AUX battery isolation relay is missing from your list of changed parts.

Celicasaur

HUDS_E500

Well the brake ~ visit workshop light was the SBC, and talk about luck, I got it diagnosed before the 30th of this month which is the time when the MB warranty (fix it for free) expires. THANK GOD! So it is at the MB dealership and they are awaiting the new SBC to arrive tomorrow.

One down now the battery..

spinn

Good news on the SBC. I'm sure the dealer will be happy to address your battery issues. :P

HUDS_E500

Haha im sure theyre thrilled.. Im sure its a pain to fix but rather them cough up the $ to fix it rather than me.. Sure MB pays them back.. But theyre telling me it is a newer upgraded unit? I got about 130k out of this one, so i hope to god it is "new and improved"

vettdvr

Can you get a part number on the new SBC system so we can see if there are any changes on the numbers? the number should be on the invoice.