isabella_bauer42

Mercedes A Klasse Diesel Starting Problems

My 2003 Mercedes A Klasse with a diesel engine struggles to start. Mileage is at 104397 km. I've identified an interrupted continuous plus on Terminal 30. Could this be a heavily discharged or defective battery? I suspect a voltage drop somewhere. I have checked the Wiring Harness, but couldn't spot any issues so far. Starter Motor seems fine. Power Supply looks normal as well. Any ideas?

4 comment(s)

I had a similar issue on my Mercedes some time ago. It turned out to be a faulty Ignition Switch causing excessive drain, even when the car was off. Check for parasitic draw. It's like a slow leak in a tire; even a small one will eventually leave you flat. Have you load tested the battery?

Thanks for the hint. Load test confirms battery is heavily discharged. Where exactly did you find the Ignition Switch issue? Was it obvious or did you need special tools?

It wasn't immediately obvious. The switch seemed to function normally, but current leakage was present. Diagnosis required a multimeter and some patience. If you already have a heavily discharged battery, replacing it might solve the issue temporarily, but the root cause will still be there. I would recommend taking it to a workshop.

Thanks for the detailed explanation. You were spot on. The workshop confirmed a faulty Ignition Switch causing the battery drain. Repair cost was around 290€. Car starts perfectly now.

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