My car very recently started some bizarre issues only when I take a corner sharply (pulling into office parking lot from road that has 50 mph speed limit, highway exit cloverleaf ramps, etc). I get the ESC fault, adaptive headlight faults most frequently, also occasionally ABS, etc, the cluster resets, I feel the power steering kick off briefly, as does COMAND and my radar detector. As soon as i'm back on the gas, it all comes back to life. Sometimes the warning indicators stick around until the car has been restarted.

The car has started fine although admittedly a bit more sluggishly than I would expect but nothing substantially out of the norm from the last year of ownership.

I hooked the car up to star and cleared the faults (engine off voltage was 11.9/12ish per STAR). I wasn't able to run as many diagnostics as I would have liked due to an impatient girlfriend who naturally was with me when I was close to the shop (where I have access to the Star computer). Due to the sheer number of codes, I'm pretty confident it is a battery issue. I will replace it tomorrow/tuesday depending on availability from my local supplier. It was also worth noting that after 15-20 minutes of the engine off and star hooked up the car needed to be hooked up to a charger briefly before restarting.

I'm mostly curious (as I can't test run with the battery alone) if this makes any sense as far as the times of occurrence. If it was a battery issue alone, logic would tell me that it wouldn't restart after the engine is off and the car has been sitting over night. Also, if it was a matter of having my foot off the accelerator/alternator, I'd expect the same symptoms when coasting, sitting at a stop light, etc.

Any ideas or insight would be greatly appreciated.

Thank you!

 

Side note, the battery itself, nor connections at the battery itself are loose. That brief epiphany sadly was not the issue.

 

Way over my pay grade here, but it could be that the battery has somehow become low on electrolyte. It may have a cell going bad. So when you corner, the G force on the electrolyte causes it to uncover more of the plates in the bad cell, causing a temp voltage drop. The continuous need to charge it is also an indication of a bad cell. The electrical continuity is compromised preventing proper charging. Low voltage causes all kinds of problems as you have noticed. My wife's 2006 Infiniti actually had a battery that required water. They called it low maintenance as opposed to no maintenance. It was under a cover and had never been checked for fluid until the morning the car wouldn't start. Good luck and keep us posted.

 

I think it would be worth replacing the battery just to eliminate that as a possible cause. Tracking down electrical issues is never fun but I think the battery is a good place to start.

 

Very intriguing concept. I admittedly don't know a ton about the technology of batteries. It is an MB VRLA OEM one. I haven't determined how to interpret the date stamp as of yet but it looks very new. I'm planning to check it with the local dealership tomorrow before coughing up cash for a new one.

I will certainly report back with any updates.

Not the added extra expenditure I had planned. Already this month, I am planning to knock out a full brake service, check over steering components, replace both rear air springs (they leaked last winter when it was cold), and replace the tranny fluid and filter (43k miles on the car) + another oil change. I'd hoped to get some PDR and touch up work done from the misc parking lot warfare it's been exposed to over the past year of living/working in the city. I'm adding a battery to the ever growing list! Tune/Tint/Exhaust would have been so much more fun!

 

While running the battery isn't doing much except staying connecting and getting a trickle charge. Seems like an alternator issue if you are getting sub12v while running. Should be 12.6 or higher. Do you get any of the warnings if you floor it? Just thinking about how the alternator acts while it's under load.

 

I'm sorry for the confusion, that voltage was engine off, ignition on for a quick scan with star. Was sub 12v immediately after turning the car off and connecting the computer. That was not the voltage with the car running

 

So what was the voltage with the car running?

 

Just checked... battery tested "good" but 49% charged, engine on, in the 14's and stable over a minute or 2. Same symptoms occured pulling back into my office. Warning's for esc, stability, every brake warning, and center of dash turned red briefly... pulled forward, they all went away. It's the strangest thing I've ever experienced with a car...

 

I still bet on the battery, but get the alt checked as thefisch suggested. The alt does not make electricity on it's own like a generator would. It takes a small amt of electricity from the battery and magnifies it to 14 v via mechanical energy. It puts more back in than it takes out. So if the voltage is around 14 with the car running but the battery won't charge, the battery is likely resisting the charge due to a bad cell. BTW back in the day you could push start a stick shift gen equipped car with a completely dead batt. Clutch in, push it as fast as you could get it to go, pop the clutch, and it would start as long as nothing else was wrong. Of course, the low men on the totem pole got to do the pushing....

 

thats weird i see it going up to 14.9v like 2 or 3 times... but usually its at 12.6 in 95% of times.

 

could it be a bad belt?
most likely not , but..

 

Oh I see, probably not alternator then. Start with battery like pjw1967 suggested.

 

The reading will jump around when the engine is running as the internal regulator senses changes in load. 12.6 is the voltage when the engine isn't running.

 

ummmm i get 12.6 when engine is running...i mean it jumps to 12.7-8-9 but its at 12.6 almost all the time while driving

 

Turn on the a/c and headlights and see what happens. How old is your batt?

 

lol still at 12.6 but ill double check out if curiosity. battery is about 6 months old. i trickle charge here n there

 

I worked at Advance Auto parts for a few years and saw a ton of batteries. Bad batteries will often test "Good" even though there is a bad cell. The fact that your battery is showing 49% charge indicates to me that it is resisting a charge like someone else already mentioned. Definitely replace the battery first because it's the easiest solution. THEN if you still have problems you can diagnose it further knowing you have a decent battery.

 

Pulled the battery and charged it with a snap on charger to 99%. Voltage was abmormally high. I then checked it immediately whole out of the car and it said good - needs to be charged. Despite being 1 year old Mercedes won't warranty it due to this fact. I replaced it with a Napa agm. So far, problem is solved. Cleared all codes with star and drove like an a-hole... will report back after a few days if it stays in the smooth sailing front!

Thank you all. It was really a peculiar symptom. One I had never head of for sure.

 

I had to replace my battery the 2nd week after I bought the car. Fortunately for me it died quickly and my car wouldn't start so I knew right away what the issue was. I opted for the standard battery as I got a longer warranty over the AGM which they didnt have in stock at the time. I spoke with a mercedes service advisor and he said that using a standard battery would be perfectly fine as long as the CCA and other ratings matched. Just adding that in case anyone was wondering. My car is running great since the install

Good to hear that you got it solved!

 

I debated going with a non agm battery. 900 vs the 850 cca agm, and a LOT cheaper (110 vs 175). I live in the Midwest and the bit of online reading I'd done made me inclined to believe the agm ones hold up better in cold weather. I was only half convinced this was going to be the issue and figured I would be chasing a loose ground on something similar that was losing full contact when the car cornered. My fingers are crossed this fixes it so I can finally have time to do the other fall maintenance items along with some paint correction from my neighbors spray paint over spray.

 

I understand that.. I live in FL so cold weather isn't an issue lol. I would also suspect a loose ground from the symptoms you were describing. Especially since those are not typical battery issues..

The paint overspray makes me cringe so hard.. I have some paint chips on my hood that I'm going to try and fix one of these days. Still need to find a product that I'm comfortable with to fix those chips.

 

Clean with mineral spirits, let dry, dab with factory touch up paint, allow time to fully cure, carefully wet sand until flush with progressive grit papers up to around 1200 or even 2000 grit, compound, polish, and wax a lot easier than it sounds. Good luck! I'm doing the same over next month before the snow hits the ground!

 

Glad it worked out that it was just the battery OP.

That's what I get when driving for the most part. If you floor it, it should jump to mid 14v.

 

Lead Acid Batteries
Check the voltage at the battery with the engine off and after driving the car long enough to charge it. When the engine is running and the alternator is charging the voltage at the battery can reach 14.0V or more. After turning the engine off the voltage at the battery should read 12.6-12.7V fully charged. Check it one hour later and a good battery should hold at 12.6V.

12.6V 100% Charged
12.3V 75% "
12.0V 50% '
11.0V Discharged