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 Matt Your Own Question
Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 24212
Experience:  BEng hons Mech engineering, in auto industry 22 years
Type Your Mercedes Question Here...
Matt is online now

Class Eco start/stop playing up, it has been to dealer three

Customer Question

B-Class Eco start/stop playing up, it has been to dealer three times but they cannot (will not?) tell me what the problem is or show me a list of parameters controlling the function. Changed auxiliary battery twice, still not fixed! Any ideas?
Submitted: 1 year ago.
Category: Mercedes
Expert:  Matt replied 1 year ago.


you say the start / stop is misbehaving can you tell me the sequence of events? doe it just sit there cranking the engine?

Customer: replied 1 year ago.
No, the problem is that it works for a while (days, weeks) and then stops. Dealer fiddles with it, works again, then stops. The car has been in three times, dealer either does not know how they 'Fixed' it or won't tell. Says it is very complicated, 30 or more parameters involved, refuses to provide a full list, says it is copyright. When it is working, the green light comes on almost immediately after starting the engine, when it is not working the ***** *****ght stays on for days! The car is still under warranty (another three months or so) and therefore I am minded to reject it as "not fit for purpose", although there is no other apparent fault with it.
Expert:  Matt replied 1 year ago.


the reset of the stop / start needs the use of the Mercedes STAR software so even if you had the procedure you'll still need to invest in the software

however there are a few things that can stop it form working

  • Coolant Temp too high, or too low
  • The engine has not ran for at least two minutes
  • The AC is on and not in the economy mode
  • Low Vacuum
  • Battery charge low
  • High current draw on the 12 volt system (IE defogger, defroster, and windshield wipers all on at the same time)

If one of the above conditions is met it does not allow the start stop feature to work.

so I'm wondering if your dealer has investigated all these? or are they just doing a reset and sending you on your way

as if the engine has a vacuum leak then this can come and go with temperature

I'd go back to the dealer and present them with this list and ask have they checked them all