Alternator or Battery?
Thread Starter
Junior Member
Joined: Aug 2007
Posts: 74
Likes: 0
E320
Alternator or Battery?
So my vehicle (1999 pre-facelift w210) is having issues starting, and it's because of the battery as the dash as well as the windows show typical symptoms. Question is, how does one diagnose where the issue lies? I've jumped the vehicle and tried charging it by running the vehicle for 15-20 minutes but it still has a difficult time starting.
I should also note that the battery is old; i do not have a date. I've owned the vehicle for about five years now and have never had an issue up until now. I do not have a reason for why the power drained as all lights and doors were off or shut. The battery is a duralast so it seems as though it was replaced at one point unless that is the OEM battery MB uses.
I've also jumped the vehicle and disconnected the battery to see if it runs off of the power generated by the alternator alone, and that was a no-go. The vehicle turned off as soon as i disconnected the positive battery terminal.
For that reason i am leaning towards the alternator being the issue. Any suggestions/comments are appreciated.
I should also note that the battery is old; i do not have a date. I've owned the vehicle for about five years now and have never had an issue up until now. I do not have a reason for why the power drained as all lights and doors were off or shut. The battery is a duralast so it seems as though it was replaced at one point unless that is the OEM battery MB uses.
I've also jumped the vehicle and disconnected the battery to see if it runs off of the power generated by the alternator alone, and that was a no-go. The vehicle turned off as soon as i disconnected the positive battery terminal.
For that reason i am leaning towards the alternator being the issue. Any suggestions/comments are appreciated.
Senior Member
Joined: Jan 2007
Posts: 484
Likes: 0
From: Südflorida
'99 E430, '05 ML500, '15 GLK350
Get a voltmeter. Measure battery voltage with car off, should be 12V. Start car and measure voltage at battery terminals, should be around 13.8-14.2 or so. If that's the case, the alternator is charging as it should.
Senior Member
Joined: Apr 2006
Posts: 463
Likes: 8
From: Long Island, NY
01 E320
Change your battery. Thats the problem. Never disconnect a battery on a running vehicle. That worked 20 years ago but unless you want to fry your engine computer or your alternator/ voltage regulator, don't do it. I always change batteries around 4 years. I learned from boating that you never get sentimental (or cheap) about batteries
