Mercedes Benz 2008 B Class

A couple days ago I took my car to a mechanic as he was having a look to check if it was worthy buying it for himself long story short he decided not to buy it . In the past days my car doesn’t turn on at all and the fan works really fast. On my dashboard I can only see the engine light and no body seems to have any idea what is going on . Please tell me what might have happened

First, ive never even heard of a mercedes B class. I assume it was never sold in the US. Second, with a 14 year old mercedes, anything could have gone wrong. You need to have it towed to a mechanic you trust.

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Who are these people that have no idea ? They must not be mechanics and the B Class was never sold here in the US . Call the mechanic who decided not to buy it , he might be able to fix it for you . Or it is off to the Mercedes dealer by tow truck.

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Chill dude I didn’t read the website rules properly so I had not idea this was about US mechanics. So be nice

What do you mean by the fan runs really fast? if the car wont start to get hot enough the fans usually do not kick on.
do you know what the code is for your check engine light?
I would check the battery first. if it is not putting out enough volts it will make the electronics act up.
also check to make sure all the fuses and relays are good.

No worries. We get posts here from all around the world, not just USA.

Are you saying your car started acting up after the mechanic inspected it? hmmm … one idea, he probably connected a scan tool to the OBD II connector to check for any diagnostic codes, current and pending. . That connector is located near the driver’s left leg. Give that area a look-see. Maybe he left something connected to the OBD II, or caused another connector in the same area to come loose.

For more ideas here, auggest to explain what you mean by “car doesn’t turn on”. Does it crank the engine ok, but not start? Or won’t it even crank? And explain which fan is turning faster than usual. Engine compartment fan?

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This Forum is not only about US mechanics but there are very few regulars from other countries. A MB B class has never been sold here and you did not provide enough detail to get much help. Is your engine gas or diesel ? Do you have Check engine light codes ?

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The radiator fan operating at high speed is an indication the engine ECU/PCM is inoperative. Could be a power supply problem, communication problem or internal damage.

US auto mechanics don’t mind answering questions however there are few mechanics on this message board.

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Hello everyone thank you for your friendly help I appreciate everyone’s response! Now, when I try to turn on the car nothing happens no sign at all only the fam that starts to work really fast for no reason. What I suspect is that they installed something on the system to lower the car value for sale. Up there is a dashboard photo of what I see when I try to turn on my car.
Thank you all

The engine light is supposed to turn on with the key in “on”, before the engine starts. I expect that is normal. The question is why isn’t the engine starting?

I presume you don’t hear the rrr rrr rrr sound with key in “start”, normal sound associated with cranking. Possible causes

  • Battery charge low
  • Transmission Neutral safety switch failure
  • Ignition switch/starter relay/starter motor failure.

Ask your shop to give a quick check for those. If problem remains ask your shop to measure the voltage at the starter motor during cranking. The B wire (thicker) and the S wire (thinner) should both measure at least 10.5 volts. Usually once that number known the shop can figure out the cause.

Unlikely shop tech disaabled your car so you’d sell it at a lower price. But they may have inadvertently done something, like forgetting to re-connect a connector. Suggest to ask them to double check.


Thank you very much I appreciate it! Everything noted👍🏻

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