Question about 2001 Mercedes-Benz C-Class

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The following fault is be shown on my display screen "UNDERVOLTAGE CONSUMER DEFECTIVE".

What fault does my car have? I am not sure what that sign means. Does my battery need charging?

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

Posted on Nov 06, 2008


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I got a c-class mercedes and on my dash board today appeared UNDERVOLTAGE CONSUMER DEFECTIVE. what can i do?

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1 Answer

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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

1 Answer

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.

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

3 Answers

Undervoltage consumer defective

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.

Nov 06, 2008 | 2001 Mercedes-Benz C-Class

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