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Hello all, I have a higher mileage 2014 E350 that I've been enjoying, but today it didn't start on after lunch break. The car isn't parked inside a garage at any of my normal destinations. Here are the events leading up:
A typical work day is driving to work in the morning, then at lunch drive to the gym and workout for an hour, drive back, and finally leave at 5.
Monday: 0f most of the day. Started fine in the morning, started fine driving to gym, started fine driving back, started fine driving home
Monday: 0f most of the day. Started fine in the morning, started fine driving to gym, started fine driving back, started fine driving home
Wednesday (today): 0f to start the day, 15f at lunch time. Started fine in the morning, started fine driving to gym. Leaving the gym, the engine wouldn't even turn over, just clicked a few times and would give up.
Jumped it with a coworkers car, got back from the gym, and messed around with the menu a bit to get voltage on my dash, confirming what I already knew the battery was low (11.8v). Tried starting it again for kicks and saw the voltage drop in real-time with every click . I didn't have time to drive it around to charge up the battery, so I accepted my fate that I would have to jump it coming home. (in retrospect, my time would have been better spent driving around rather than having it off trying to open the Vehicle Data hidden menu).
I get out of work, and it starts right up. What gives?
If a bad battery, I'm confused why sun, mon, and tues were fine in worse conditions (colder battery, cold start engine). My best guess is the alternator may be failing to charge the battery fast enough, and 2 starts close to each other with little driving in between mean the battery had little time to recover on its own, but this doesn't really explain the previous successes in my mind, unless I'm observing it get worse and worse as the week goes on. I am quite confident I did not turn any interior lights on during my drive to the gym today so I don't think it's that (besides, they should turn off anyway as I understand it).
The car reported about 8.5A draw with after turning the car off along with switching the lights to off when I got home tonight (sadly forgot the voltage).
Are there any common causes of such a problem? I plan to monitor the voltage via the gauge while driving to see if it's in the 14v+ range as I understand that's what it should be.
Last edited by yottabit; Jan 22, 2025 at 07:23 PM.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
How old is the battery?
Toward the end of this video (which is worth watching), the guy says modern alternators are NOT designed to charge a fail or failing battery, only to keep a healthy battery charged.
I drove 2hrs after getting home from work and noted the cars voltage, it was 14.8v steady while driving. I did try and find out how old the battery was but I could not see a date sticker on it. I actually have a spare one from mid 2023 that I can swap in. If the battery is dieing I'm still confused why it started find the first few days of the week.
If DC electrical system goes intermittent bad like your starting issue, at the least inspect all the main ground wire and its connection first.
It is a 12 years old car today, so the undocumented under the car W-TF main ground would need some cleaning/inspection/tightening.
You could have a "tired" battery, but poor high power electrical connection will amplify problem and shorten a good battery life.
simple battery check.
Fully charge it.
Then watch volt meter when starting engine.
While starter is spinning the voltage needs to be above 9VDC.
Any lower computers go wonky and starter might not have enough ooomph to spin engine over long enough to start
If not take it out fully charge it and go to auto parts store for them to properly test it on a battery tester.
They will let you know for sure.
I drove 2hrs after getting home from work and noted the cars voltage, it was 14.8v steady while driving. I did try and find out how old the battery was but I could not see a date sticker on it. I actually have a spare one from mid 2023 that I can swap in. If the battery is dieing I'm still confused why it started find the first few days of the week.
Batteries are like 5-year olds -- unpredictable and unable to explain their behavior. Go to an auto store and have someone load test your battery. If it's shot, they'll be happy to install a new one. A couple hundred $$ beats jump starting on every trip.
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. I didn't have time to drive it around to charge up the battery, so I accepted my fate that I would have to jump it coming home. (in retrospect, my time would have been better spent driving around rather than having it off trying to open the Vehicle Data hidden menu).
