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How to replace alternator on a Mercedes Benz E C CLK SLK S Class

How to replace the alternator on a Mercedes Benz.

Got a warning on your instrument cluster saying Battery/Alternator Defective Visit Workshop! It is very likely that you need a new alteration. Check the battery first and if that is in good condition than you may want to consider replacing the alternator. In this article we will show you how to replace the alternator on a Mercedes Benz. Replacing the alternator at the dealer can cost you over $1000 but if you do it yourself, you can do it for as little as $90, so keep on reading. It’s not a complicated job and we know you can do it. These instructions apply to most Mercedes Benz models with the V6 M112 and V8 M113 engines.
For this job you will need to have a set of Female E Torx Tool Set which you will need to remove the two bolts that hold the alternator in place. Below is a picture of these sockets and if you need a set you can find them on Amazon for under $20.
female torx socket setamazon check price

Step by step instructions on how to replace the alternator on a Mercedes Benz

Applies to C Class , E Class, CLK Class and many other models with the V6 M112 and V8 M113 engine.
    1. Open the hood.
    2. Disconnect the NEGATIVE terminal from the battery. HINTS: Locating the battery. Depending if you have a C / E / CLK class it could be either in the engine bay compartment, under the rear seats, or in the trunk. In our case we are working on a C Class W203 2001-2007 and the battery is located in the engine bay. First we need to remove the cabin air filter housing. Push up the 3 clips shown in the picture below and pull out the housing. accessing the battery on a mercedes benz c class_mercedes_Benz
    3. Remove the bolt on the NEGATIVE battery terminal clamp and disconnect the cable. You will need to loosen the 10 mm bolt, no need to completely remove the bolt. DSCN0584_mercedes_Benz
    4. Remove the engine cover. It comes right up. It’s has clips that hold it in place and no screws.remove engine cover
    5. Remove serpentine belt.  Read this article and watch the video on how to replace the serpentine belt.
    6. Remove the cap from the back of the alternator. This is the electrical cable which is part of Circuit 30. Alternator is identified as G2 on electrical schematics. mercedes bosch valeo alteranor_mercedes_Benz
    7. You should see a nut. Remove the 13mm nut on the back of the alternator. See the close up picture below. positive cable to alternaor on mercedes benz_mercedes_Benz
    8. Unplug the connector that goes into the back of the alternator. Pres on the tab and pull it away from the alternator. unplug the connector alternator_mercedes_Benz
    9. Remove the two bolts that hold the alternator in place using the Female E Torx sockets we listed on the required tools section above.serpentine belt on alterantor pulley_mercedes_Benz
    10. Remove the alternator. It won’t be easy to remove it but you can do it. You may have to use some force in this process. This step won’t be fun. pulling out the old alternaor_mercedes_Benz
    11. Install the new alternator. Here are a couple of pictures of our new alternator which we bought for $115 on Amazon. If you need to find a replacement alternator at a fraction of dealer prices and even cheaper than your local parts store check Amazon, click here.  order now on amazon
      back of mercedes alteranor_mercedes_Benz cost of new mercedes benz alternator_mercedes_Benz
    12. Install the new alternator and tighten the two bolts to 42 Nm.
    13. Connect the electrical cable to the alternator. Tighten the nut for the electrical cable ( positive +) between 15-18Nm.
    14. Plug the electrical cable on the back of alternator and make sure it clicks when you push it in. That way you know it is locked in place.
    15. Reinstall the serpentine belt, the engine cover and the reconnect the battery.

Torque Specifications

  • 2 Bolts that hold the alternator in place. Max 45  Nm.
  • 1 Bolt on the back of the alternator. Between 15 Nm to 18 Nm.

How much does a Mercedes Benz alternator replacement cost?

The answer depends on where you live. With that in mind we will give you a general idea. First is the price of the alteratnor. If you buy it at the dealer you can will end up spending around $1000 to replace the alterantor. If you do it yourself you will can save hundreds and replace the alternator for 1/10 of that. How?

First buy the alternator itself online from your favorite online retailer. You can find a new alternator online  for $100 to $200, find one for your Mercedes Benz on Amazon, see link here. The one replaced we bought on Amazon for $115 and worked out great.
Replacing the alternator on a Mercedes Benz should not take more than 2 hours. If you are doing it yourself for the first time you should be able to do it in around 3 or 4 hours, so plan on a Saturday morning. An experienced mechanic should be able to replace the alternator in even an hour. Even Valeo or Bosch alternators with are the Original Equipment installed on the Mercedes Benz cars, can be bought for a fraction of  what the dealer charges. For example check out the links below. We would appreciate if you click on these links even if don’t buy one.check-price-at-amazon

Applicable Models 

Years: 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
E Class Models: E320 E430 E55
C Class Models: C240 C320 C32 C280
CLK Class: CLK320 CLK430 CLK55
SLK Class: SLK320 SLK32 AMG R170

Related Part Numbers

Bosch Alternator 12 120 Pulley Rotation Polarity
Bosch 0124515046, 0986042550, 0124515132
Delco DRB2550
Chrysler 5097755AA, 5097756AA
Mercedes 0111546802, 011-154-72-02
Mercedes A011-154-68-02, A011-154-72-02
Valeo 2542317, 437222, 542317, SG12B021
Bosch 0-124-515-056, 0-124-515-132, 0-986-047-540

Please use the comments section below to let us know how your job went. Feel free to post any recommendations or suggestions to help others. 

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