Mike Podar

Hi, I drive a 2012 C250, 125k miles (well, my wife drives it). About a month ago an issue started. Engine wont start, no crank, at various times (either morning or before return from work, cold engine). But after a few minutes would start fine. One day it just didnt want to but was able to resurect using a portable battery. Took to MB service. They said battery was dead. Changed the battery, all computer tests ok after that. Car ran fine for a few days. Then, issue started again. Erratic startup issue, after insert key the dashbord lights up, key sound, but no engine start, no lights or horn. It would start with jumper cables. Took it to independent European car service, supposedly a Mercedes-trained technician too. They kept car for two days, never able to reproduce the issue, charged me $140 and suggested to replace a relay as a possible source of issues (worksheet is in the car so dont know which "relay"). I agreed, took car back, started fine from cold for two days. After going weekend shopping and driving it for an hour, it would not start again in parking lot. This time jumping it would not work either, from another car battery. Tried it twice over about 45 minutes wait. Called for towing and while waiting for them, gave it one more change and it started in one try with the key. Took it straight back to service and left it there, but i fear in the morning they will be able to start it and again not find the problem...

One thing that is consistent is that when it wont start, the electrical issue is also on horn and lights (but not on the radio). Maybe amperage draw difference, or are there multiple levels of electric startup stages. Why did it refuse to jump start for almost an hour but then started on its own? Some temperature sensor that needed to cool down? Was that coincidence? I also had the issue in the morning with everything cold, so dont get it. What can I suggest the service people to do?

Thank you, thank you :)

Mike

Update: The technician identified the issue, a failing component in the ignition startup module. MB doesnt provide that separately, but apparently they can rebuild it. The whole thing takes two weeks and will cost close to 2k in part and labor. Considering this car is not even a teenager (10 years old) and 125k, to have such problems, which apparently happen in even younger cars, is appalling. That is called poor component design and workmanship. Looking forward to a point where I will be forced to get rid of it and never buy a MB again...

Mike

CaliBenzDriver

Mike, sorry to read about your repeated car troubles. MB standard failures are designed in multiple tiers and difficult to identify for non specialised shops.

What you have is called a "No crank, no start" condition. In order to focus on solutions you need to scan the car for obvious faults.

Low voltage is an excellent provider of glitches that soft-crash the main power Mgt computer (F-SAM) that in turn causes additional voltage drain. These MB cars are well capable of frying a fresh AGM battery if root cause is not diagnosed properly. Collect evidences to guide your actions.

My short list suggestion for your research:

• Ignition Switch
• Steering Lock
• low voltage drain

Scan the car will save your resources.🤞