How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Mike Your Own Question

Mike
Mike, Mercedes Technician
Category: Mercedes
Satisfied Customers: 39198
Experience:  Tech Expert
9261905
Type Your Mercedes Question Here...
Mike is online now

Just drove my sl(###) ###-#### first time in 2 weeks. Battery

Resolved Question:

Just drove my sl(###) ###-####for the first time in 2 weeks. Battery light cone and says visit workshop, and the battery charge goes up to 8kw when driving and down to 0 when stopping, now my engine management light has just came on as well
Submitted: 1 year ago.
Category: Mercedes
Expert:  Mike replied 1 year ago.
Hello and Welcome..

My name is ***** ***** Im happy to help..

With this fault as you describe it, it sounds like the alternator( or its circuit ) has developed a fault... but - the battery itself should be checked first. This should be done by first fully charging the battery and then have it pro tested at a local garage. If the battery has suddenly failed, as they can do , that will cause what you have so that should be checked first.... a new battery would be the answer then.

If thats ok though - a proper test of the alternator output will find the fault. You should have circa 14.6 volts to the battery on a meter test... anything 12v or under or 14.8 / 9 or over, will be a charge circuit / alternator fault.

So thats the way to work through / get this sorted for you.

Of course - check the cabling /connections and alternator drive / belts first also.

Such erratic power -through / battery etc faults will cause the EML / engine light also - so once thats cured , likely as not, that will go off too.

If not - then a plug in diagnostic test would be required to check why thats on.

Let me know if you need anything else at all.. If you do get back to me, I will get back to you asap thereafter.

Meantime , please do now at this point, click on the "Excellent ratings" for me... I really appreciate that and Thank you....

Kind Rgds, MIKE..
Mike, Mercedes Technician
Category: Mercedes
Satisfied Customers: 39198
Experience: Tech Expert
Mike and other Mercedes Specialists are ready to help you
Customer: replied 1 year ago.
Thank you. The eml has now gone off. So it's either the battery or the alternator. I will get it checked tomorrow. It is driving ok. But will try battery first. Then your other suggestions thanks

What Customers are Saying:

 
 
 
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
< Previous | Next >
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
  • Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible. Charles
  • As a single woman, I really appreciate an excellent and affordable opinion.
    Thank you Geordie, I will not hesitate to contact justanswer in the future!
    Sue
  • Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff. Jim
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C.
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex
 
 
 

Meet The Experts:

 
 
 
  • Matt

    Matt

    Mechanical Engineer

    Satisfied Customers:

    483
    BEng hons Mech engineering, in auto industry 22 years
< Previous | Next >
  • http://ww2.justanswer.com/uploads/35/350matt/2012-6-7_182356_matsavatr.64x64.jpg Matt's Avatar

    Matt

    Mechanical Engineer

    Satisfied Customers:

    483
    BEng hons Mech engineering, in auto industry 22 years
  • http://ww2.justanswer.com/uploads/EU/eurotec/2012-6-11_13153_mpjaphoto.64x64.JPG Marty's Avatar

    Marty

    ASE Certified Technician

    Satisfied Customers:

    21378
    Bosch Certified Master Technician with over 35 years experience in the automotive industry.
  • http://ww2.justanswer.com/uploads/MI/mikeamechanic/2013-4-2_175558_photo.64x64.JPG mike_a_mechanic's Avatar

    mike_a_mechanic

    Mercedes Mechanic

    Satisfied Customers:

    116
    17 years experience as a auto mechanic, foreign and domestic.5 years running my own repair business.
  • http://ww2.justanswer.com/uploads/MB/MBpaul/2013-8-21_204936_paul.64x64.jpg MB Paul's Avatar

    MB Paul

    Mercedes Technician

    Satisfied Customers:

    212
    Mercedes Benz Qualified Diagnostic Technician
  • http://ww2.justanswer.com/uploads/IN/indytech/2013-8-8_102717_SantoDomingo146598x6402.64x64.jpg Greg's Avatar

    Greg

    Technician

    Satisfied Customers:

    1081
    Automotive diagnostic tech
  • http://ww2.justanswer.com/uploads/TE/techmachine/0601821347169_717372168_8940977_39623330_o.64x64.jpg Ross's Avatar

    Ross

    Diagnostic and repair technician

    Satisfied Customers:

    453
    Licensed diagnostic and repair technician