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Mercedes-Benz Alternator Replacement V6 M272 - V8 M273

DIY Cost: $100-$250
Est. Time: 2 hr
Difficulty: Intermediate


This guide provides instructions on how to replace the Alternator on a Mercedes E C CLK S ML GL R Class with the M272 and M273 engines. 


What you will need




  1. Park the vehicle on level ground and set the parking brakes.
  2. Allow the engine to cool down.
  3. Pull the hood release under the dashboard and open the hood.  Secure the hood with the hood support. support hood
  4. Locate the battery in the engine bay, trunk, boot, or under the seat and disconnect the negative battery terminal. Battery in BootBattery Location
  5. Create a diagram of how the serpentine belt is routed on the different pulleys.routing


  6. Loosen the serpentine belt by using a 17mm socket to twist the tensioner bolt counterclockwise.releaseTensionerSlide the belt off it.Mercedes tensioner release


  7. Spray penetrating oil to the alternator retaining bolts and wait for 15 minutes for ease of removal.
  8. Remove the alternator ground wire using a 12mm socket. Alternator positive connection cableremoveGround
  9. Remove the components blocking your access to the alternator, like the engine plastic cover, hoses, power steering fluid reservoir, and the overflow reservoir.Remove hosesRemove engine plastic cover
  10. You may look at the alternator below to understand how it is connected to the engine.

  11. Loosen four (4) alternator retaining bolts using an E12 socket.removeAlternatorbolts


  12. Unplug the alternator's electrical connector from the back of the alternator. removealternatorsocketDisconnect alternator connector mercedes benz r-class ml-class e-class


  13. Using both of your hands, you have to move the alternator side to side while pulling it up.Remove Alternator
  14. Position the new replacement alternator.
  15. Connect the alternator positive, ground, and electrical connector.
  16. Connect the negative connector using a 12mm socket. Re-attach the rubber cap(if any).Alternator positive connection cable
  17. Mount the alternator using 4 retaining bolts. Alternator Mercedes-Benz


  18. Twist the tensioner bolt counterclockwise and reposition the serpentine belt.
  19. Reconnect the battery.
  20. Start the engine and check voltage. With the engine running, you should be getting between 14.0 and 14.7 volts.

Frequently Asked Question

How do you know your alternator is bad?

  • A common symptom of a defective alternator is when your battery light is on while the engine is running.

How much does it cost to replace a Mercedes Benz Alternator? 

  • The average cost to replace a Mercedes Benz Alternator is between $447 and $800. Labor costs are estimated at around $386, while parts are priced between $350.

How long does a Mercedes Benz Alternator last?

  • The average life span of an Alternator is about 6 to 10 years. It depends on how many miles the vehicle is regularly driving and how many aftermarket accessories the owner have installed, which may cause the alternator to work overtime.

How to test an alternator?

  • Using a voltmeter, connect your positive lead to the battery's positive terminal and negative lead to the battery's negative terminal. It would be best to get 14 v to 14.8 v, which means your alternator is working properly.

Can you drive a Mercedes with a faulty alternator?

  • It is not recommended to drive the car once the check battery light is on since it is more likely that the car would stall after a few minutes.


Mercedes-Benz vehicles are equipped with an M273 engine.

M272 engine

  • 2004–2011 R171 SLK 350
  • M272 IN SLK R171.jpg
  • 2004–2010 W219 CLS 350
  • 2005–2010 C209 CLK 350
  • 2005–2007 W203 C 350
  • 2007–2011 W204 C 350 / C 350 4Matic
  • 2011–2015 W204 C 350 BlueEfficiency / C 350 4MATIC BlueEfficiency
  • 2005–2009 W211 E 350 / E 350 4MATIC
  • 2009–2011 W212 E 350 / E 350 4MATIC
  • 2005–2013 W221 S 350
  • 2005–2012 R230 SL 350
  • 2006–2017 W251 R 350
  • 2006–2011 W164 ML 350
  • 2005–2014 W639 Viano (known as the M272 978 in China)
  • 2006–2013 NCV3 Sprinter
  • 2008–2011 CL203 CLC 350
  • 2008–2012 X204 GLK 350

M273 engine

  • 2006–2011 E 500 / E 550
  • 2006–2010 CL 500 / CL 550
  • 2006–2010 CLS 500 / CLS 550
  • 2006–2012 GL 500 / GL 550
  • 2008–2011 ML 500 / ML 550
  • 2006–2009 S 500 / S 550
  • 2007–2012 SL 500 / SL 550
  • 2006–2009 CLK 500 / CLK 550
  • 2006-2015 G 500 / G 550
  • 2007–2012 GL 450
  • 2007–2013 S 450
  • 2007–2011 ML 450


Mercedes-Benz Alternator Replacement V6 M272 - V8 M273 Symptoms The battery warning light stays Engine stalls. What you will need Parts Mercedes M273 Alternator Tools