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Q: Not starting a month after replacing battery

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Car is not starting. It has sat in my garage for a long time. Initially, I was told it was the battery. I replaced the battery and it worked, but a month later it is doing the same thing.

The information that has been provided for your Mercedes is limited which unfortunately makes it difficult to point you in the right direction. So I see originally that a bad battery was the first culprit. Allowing a vehicle to sit for a long period of time with the battery connected can cause the computer to slowly drain the battery. It is possible that this exact thing has occurred again after replacing the battery. One thing you can try is to have a friend help you jumpstart your vehicle. If you are able to get the vehicle started this way, it is likely that either the Mercedes has not been driven enough and that the car’s computers are draining the battery power, preventing it from starting. It is also possible that you may have a parasitic draw on the electrical system. A parasitic draw is when a component in the vehicle draws excess power from the battery, even when the key is off. To be 100% certain on why your Mercedes is experiencing this issue, it may be time to enlist the assistance of a certified mechanic. They will be able to perform an electrical diagnostic on your C240 and identify exactly why your Mercedes is having trouble starting. They will also be able to assist you in making the repairs necessary to prevent this situation from happening again.

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