Electrical issue
Thread Starter
Newbie
Joined: Jan 2017
Posts: 8
Likes: 2
From: RVA
MB: 2012 C63, 1986 300e, VW: 2013 Tuareg TDI, 2002 GTI
Electrical issue
Hi guys,
Trying to narrow this down, but the basic diag process I've got in my head for this isn't giving me quite the definitive answer I'd like.
2012 c63, 60k on the clock.
Car can sit for 3 weeks, and start just fine, so even though i'm pretty sure it's the original battery, don't think that's it.
After regular daily driving, on/off/errands etc, it starts to struggle turning over - which would point me to alternator, but I don't see any other blatantly obvious symptoms of a dying alternator, also, 60k on the clock, seems early...
Is there anything else in the electrical system that would interfere with charging?
Thanks for any input!
-------------
Edit: got into the service menu. UB, idle holds 14.5-8 just fine, except for just off idle. Can't make any sense of IB, which is showing anywhere from 2-4A at idle (no major jumps turning on seat heaters/stereo etc), 10a off start, and all over when driving. I've looked, but can't find a good measure of that specifically is. Battery date code, 17Q?
So, alternator is pushing voltage just fine, battery's presumably not that old, but I can't find a definitive date code decoder either. Something with the starter perhaps? Last time I had issues with it car would've been at operating temp, so the starter would've been hot.
--------------
Edit 2: starter heat soak?
Trying to narrow this down, but the basic diag process I've got in my head for this isn't giving me quite the definitive answer I'd like.
2012 c63, 60k on the clock.
Car can sit for 3 weeks, and start just fine, so even though i'm pretty sure it's the original battery, don't think that's it.
After regular daily driving, on/off/errands etc, it starts to struggle turning over - which would point me to alternator, but I don't see any other blatantly obvious symptoms of a dying alternator, also, 60k on the clock, seems early...
Is there anything else in the electrical system that would interfere with charging?
Thanks for any input!
-------------
Edit: got into the service menu. UB, idle holds 14.5-8 just fine, except for just off idle. Can't make any sense of IB, which is showing anywhere from 2-4A at idle (no major jumps turning on seat heaters/stereo etc), 10a off start, and all over when driving. I've looked, but can't find a good measure of that specifically is. Battery date code, 17Q?
So, alternator is pushing voltage just fine, battery's presumably not that old, but I can't find a definitive date code decoder either. Something with the starter perhaps? Last time I had issues with it car would've been at operating temp, so the starter would've been hot.
--------------
Edit 2: starter heat soak?
Last edited by KGc63; Oct 28, 2018 at 01:59 PM. Reason: Additional info.
Junior Member
Joined: Aug 2010
Posts: 47
Likes: 5
2008 C300
I had electrical issues intermittently for a couple of years. MB service checked battery and alternator, but did not find a fault. Out of desperation, l had the alternator replaced at an Indy shop. No more problems.
Super Member
Joined: Aug 2011
Posts: 861
Likes: 38
From: Philly area
350 GLK, C280
Could be leaky injectors filling the combustion chamber after a stop. Makes it hard to start due to raising the cylinder pressure with liquid but after a while the fuel evaporates and the compression is back to original.
Also could be a faulty starter motor which doesn't have full power when it is hot.
Also could be a faulty starter motor which doesn't have full power when it is hot.
