Mercedes-Benz Voltage Regulator Replacement Diesel OM642

In this guide, you will learn how to replace the voltage regulator on a Mercedes-Benz alternator.

Difficulty: Intermediate

The OM642 engine found on this R-Class is also found on many other Mercedes-Benz models, including E-Class, Sprinters equipped with the 3.0L diesel engine. For more help, see the application chart below. 

Symptoms:

Common symptoms indicating a problem with your Mercedes Benz alternator includes:

  • The red battery light stays on
  • Dead battery

What you will need

Parts

Tools

Procedure

Replacing a voltage regulator on a Mercedes Benz with an OM642 engine requires two main steps, removing the alternator from the engine and voltage regulator replacement.

Removing the alternator from the engine

  1. Park the vehicle in a flat, safe place.
  2. Turn off the engine and wait for 15 to cool down. This is to avoid burn injuries while removing the alternator.
  3. Open the hood by going inside the vehicle and pulling the hood release lever.
  4. To lift the hood, go outside of the vehicle, release press or pull the hood lock, and lift the hood.
  5. Remove the negative side of the battery using a 10mm socket. You can find the battery on the trunk, inside the trunk, behind the back seat, or under the matting on the driver's side.
  6. Sketch how the serpentine belt is routed.
  7. To release the belt, use a 17mm socket and a breaker bar. Place the socket on the tensioner bolt and turn it towards your left while sliding the belt off.
  8. Using an E-10 socket with the breaker bar, loosen the alternator's upper and lower retaining bolt.
  9. Completely remove the alternator's upper and lower retaining bolt by using a ratchet and an E-10 socket. Turn the ratchet counterclockwise to remove the bolt completely. 
  10. Pull the lower retaining bolt out, then pull out the upper retaining bolt.
  11. Disconnect the electrical connector from the alternator.
  12. Using an 11mm socket, ratchet, and extension, loosen the ground connection from the alternator. 
  13. Take out the alternator for servicing.

Voltage regulator replacement

  1. Remove the alternator cover by detaching an 11mm nut and a 15 mm nut.
  2. Remove alternator cover's retaining screws using a Philips screwdriver.
  3. Set the alternator cover aside; you can now have access to the voltage regulator.
  4. Remove 3 Philips screws that hold the voltage regulator in place. Take note of the different lengths of the screws.
  5. Pull the voltage regulator off.
  6. Compare the new voltage regulator with the old one before installing it. You might find that the carbon leads are longer on the new one; don't worry because this is expected.
  7. Install the new voltage regulator by pushing the carbon leads in, aligning the voltage regulator's copper connector on the left bolt, and sliding the voltage regulator in.
  8. Reinstall the regulator retaining screws using the Philips screwdriver.
  9. Reinstall the alternator's back cover using a ratchet, an 11mm socket, and a 15 mm socket.
  10. Reinstall the alternator cover's retaining nuts.

Alternator Reinstallation

  1. Insert the alternator near its mounts, reconnect the electrical connector and the ground connector nut.
  2. Remount the alternator by reinstalling the lower retaining bolt first, then reinstalling the upper retaining bolt.
  3. Fasten the retaining bolts and torque to specs.
  4. Note: To fasten or reinstall a screw, a bolt, or a nut, turn it clockwise.
  5. Place the 17mm socket and breaker bar on the tensioner bolt and turn it counterclockwise while reinstalling the serpentine belt.
  6. Double-check the serpentine belt, making sure that it is properly seated on each pulley. 
  7. Start the engine and verify that the charging light is out.

Frequently Asked Questions

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 driven and driving conditions. 

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.

Application

Dodge Van               

  • Sprinter 2500 V6 3.0L 2987cc DIESEL 2007-2008
  • Sprinter 3500 V6 3.0L 2987cc DIESEL 2007-2008

Freightliner Van     

  • Sprinter 2500 V6 3.0L 2987cc DIESEL 2007-2008
  • Sprinter 2500 V6 3.0L 2987cc 2010-2018
  • Sprinter 3500 V6 3.0L 2987cc DIESEL 2007-2008
  • Sprinter 3500 V6 3.0L 2987cc 2010-2018

Jeep Truck                 

  • Grand Cherokee V6 3.0L 2985cc 182cid DIESEL 2007-2009

Mercedes-Benz Car                  

  • E280 V6 3.0L 2996cc 2007
  • E300 V6 3.0L 2996cc 2008-2009
  • E320 V6 3.0L 2987cc DIESEL 2007-2009
  • R320 V6 3.0L 2987cc DIESEL 2007-2008
  • R320 V6 3.0L 2987cc 2007-2008
  • R350 V6 3.0L 2987cc DIESEL 2011-2012
  • R350 V6 3.0L 2987cc DIESEL 2010

Mercedes-Benz Truck             

  • GL320 V6 3.0L 2987cc DIESEL 2007
  • ML320 V6 3.0L 2987cc DIESEL 2007-2009
  • ML320 V6 3.0L 2987cc 2007-2009

Mercedes-Benz Van                 

  • Sprinter 2500 V6 3.0L 2987cc 2010-2016
  • Sprinter 3500 V6 3.0L 2987cc 2010-2016

Reference

  1. Replacing The Voltage Regulator on a W211 Mercedes
Mercedes-Benz Voltage Regulator Replacement Diesel OM642 The OM642 engine found on this R-Class is also found on many other Mercedes-Benz models, including E-Class, Sprinters equipped with the 3.0L diesel engine. For more help, see the application chart below.  Symptoms: Common symptoms indicating a problem with your Mercedes Benz alternator includes: