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Matt, Engineer
Category: Mercedes
Satisfied Customers: 21620
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I own a 2006 Mercedes Benz slk 280. My car battery was dead

Customer Question

I own a 2006 Mercedes Benz slk 280. My car battery was dead and I had to charge it for 24 hours. After it was fully charge, I began experiencing some problems, such as, my drivers front window won't go up or down. Next, my convertible top won't go down, and experience transmission skipping.
What needs to be done in order to fix the problems.
Submitted: 1 year ago.
Category: Mercedes
Customer: replied 1 year ago.
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Expert:  Matt replied 1 year ago.


if the battery is more than a few years old then I'd replace it as this sounds like the battery may have a faulty cell thats dropping the voltage below what the ECU needs to work correctly

low battery voltage will give all sorts of funny faults and this needs resolving 1st

Also check that the alternator is actually charging the battery in the car by taking a battery voltage reading with the engine off then another with the engine running. The 2nd reading should be higher than the 1st and climbing steadily. And also check that the alternator is secure to the engine as this provides the ground for the charging circuit and make sure that the engine / gearbox earth strap is secure and the contacts are clean and bright.

if the alternator appears not to be working - take it to a electrical specialist and ask them to test it as sometimes you can replace just the diode pack and this will repair the alternator without requiring replacement

Customer: replied 1 year ago.
I took my car to a mechanic to check the window motor. He said that the motor was bad. With your expertise, do you think I should replaced my older battery and if so, would this prevent me from buying a window door motor.
Expert:  Matt replied 1 year ago.


if the window was working fine before the battery was discharged then I doubt that its suddenly gone bad as when the motors do go , its more of a gradual decline

Customer: replied 1 year ago.
Ok, with that said, what is your recommendation. Should I just replace the battery and go from that?
Customer: replied 1 year ago.
Basically, my window was working fine before the battery going dead. Please advise me further. Thank you.
Expert:  Matt replied 1 year ago.


yes I'd replace the battery as the next step and don't forget to check if its being charged when the engine runs

Expert:  Matt replied 1 year ago.


do you still need help?

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