Question about 2001 Mercedes-Benz C-Class

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Undervoltage consumer defective

The first problem i have is, when you check the level of oil in the engine its accurate but when you drive for a while a warning sign comes up REDUCE OIL LEVEL. The mistery is, when the engine cools down the oil will be accurate. The second prooblem is,my car was parked for about12days and befor now i seldom drive the car.UNDERVOLTAGE CONSUMER DEFECTIVE come up on the dash so i did not drive the car and i noticed the a/c was not blowing as it should.The next day the battery was down and so i took the battery to the garage for charging after which i put it back on, same problem.

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  • mjackmcd1 Dec 16, 2008

    recieved undervoltage consumer defective message. 2001 c320. Would like to know what it means.

  • spinner711 Dec 30, 2008

    I have the same problem, but my mechanic tells me its probably the imobilizer or something major. Could this be possible?



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I had the same "undervoltage, switch consumers off" message the last couple of days. Then today, another warning in red appeared "battery/alternator, see service". This was a bad sign. Luckily my car didn't stop dead in the middle of the road on the way to the shop. The service guy said the alternator was bad. p.s. my battery went completely dead about 4 months ago----this was an early warning that the alternator was going bad, but instead I just got a new battery.

Posted on Jan 20, 2009

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Reduce oil level light comes on after changing oil

Posted on Dec 15, 2008

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Regarding the first problem, there is possibly an oil level sensor issue or vehicle version coding issue(both can be more fully checked at a dealership). The second problem is not uncommon. Obviously, there could be a low voltage if the vehicle sits for a long time or is not driven alot. Sounds like the ac system lost synchronization due to lack of voltage. With vehicle running, you should be able to press and hold recirc/rest or recirc/defrost buttons on ac control panel(can't quite remember which combination). Press and hold until leds start flashing, then the ac system will go through a resynch phase. If it completes this and the led's stop flashing, then it's ok. If it does not and the led's flash very quickly, this indicates an actual malfunction of ac system adjustment motors.

Posted on Nov 13, 2008

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Sounds to me like a voltage regulator issue. This is attached to the alternator and monitors how much voltage is sent back to the battery. Any decent parts store should be able to hook up a charging system tool-most common is a Vat-40 and check the system. And they will probably do it for free. If there is an issue with the charging system, then try the voltage regulator first, as opposed to the alternator-there is quite a price difference I assure you. Let me know what you find.

Nov 18, 2008 | 2001 Mercedes-Benz C-Class

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2001 C240 ''Undervoltage Consumer Defective''

The same thing happened to me and it turned out to be the alternator. Need to replace your alternator. Easy check, start the car and check the DC voltage of the battery, with the car running you should read around 14 volts. If you are reading 12-12.25 volts then the alternator is not generating.

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i have the same problem with my 2001 C240 and my a/c does not work properly as a result.

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