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 Lou P. master tech Your Own Question
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3733
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
27644750
Type Your Mercedes Question Here...
Lou P. master tech is online now
A new question is answered every 9 seconds

I have a 2002 c240. After driving the car an hour the

Customer Question

i have a 2002 c240. After driving the car for about an hour the battery light comes on. I checked the output from the alternator and it is 14.2.
JA: Have you tested the battery? Have you tried testing the alternator?
Customer: Yes the battery and alternator are in perfect condition.
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I changed the alternator and serpentine belt and tensioner.
JA: Anything else you think the mechanic should know?
Customer: Heat seems to play a factor.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Mercedes Mechanic about your situation and then connect you two.
Submitted: 5 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 5 months ago.
Hello. Lou P here. When you checked the voltage did you have the meter hooked up to watch the voltage as the fault occurred ?
Customer: replied 5 months ago.
I checked when the battery light was on. It was 14.2.
Expert:  Lou P. master tech replied 5 months ago.
Ok I meant hook up the meter at start and watch the voltage closely and see if it goes under 13 or over 14.5. You can also watch the voltage through the service menu in the cluster.
Customer: replied 5 months ago.
It takes about an hour before the service light goes on. That is why I think it is heat related. I can check it tomorrow.
Expert:  Lou P. master tech replied 5 months ago.

ok, so here is how you can actually access the voltage screen in the dash

https://www.youtube.com/watch?v=YZtXG7IOdlk

the video has a 211 e class but its the same method for yours. you have to start on the main mileage odometer screen and make sure the doors are closed.

Related Mercedes Questions