Date registered: Oct 2003
Vehicle: 500SE AMG, E350 4matic, GL 450
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Quoted: 124 Post(s)
DIY: Changing alternator in ML 320
The following are the steps I took in changing the alternator in my 2001 ML 320. If you choose to follow this procedure, do so at your own risk.
The battery light came on in my w163 a few days ago. Luckily, I made it home before the Mercedes died on me. I did not know if the alternator needed to be changed or just the voltage regulator but being that it is the dead of winter and there is a lot of snow (a lot of snow) on the ground, I just wanted to get the ML back on the road. My alternate car is not one I really wanted to drive more than I have to in the winter.
I ordered the alternator. It arrived today. I also charged the battery before starting this procedure.
1. Disconnect battery. Remember if you have the original Mercedes stereo, you will need the code to reactivate it.
2. Remove airbox:
a. Unclip airbox at mass air flow sensor-2 clips.
b. Unclip top of airbox-several clips all around.
c. Remove air filter.
d. Gently pull up remainder of airbox. You may need to lever up the air box carefully
with a screw driver.
e. There is a plastic duct that runs from the airbox to the front of the vehicle. There is
a small faster that holds it in place. It can be undone using a trim tool.
3. Removal of fan shroud and fan
a. Note that there are two brackets that help secure the shroud. One on each side.
b. Get under vehicle. There are two internal torx bolts on each side. Undo both. Each
internal torx fits into a clip. Remove both clips.
c. Pull up on the shroud. Careful not to break the brackets on each side. You are
unlikely to clear the fan.
d. At the point at which the fan was coming into contact with the shroud, I pushed the
shroud away from me. That opened up a small space for me to get my hands into.
e. Undo the 3 allen bolts (I think 5mm) that secure the fan to the clutch.
f. Remove the shroud and the fan. I marked the front of the fan. Not sure if I needed
to but I wanted to reinstall it in the same orientation. It might only go back one
way, but I figured better safe than sorry.
g. Note routing of the serpentine belt. Draw a picture unless you have the diagram
h. Place 15 mm socket on long handled ratchet-I used a breaker bar. Place on belt
tensioner (#1 on diagram). Rotate counter clockwise until the belt can be removed
from the pulleys.
4. The alternator
a. There was a small clip that secured a cable to the area in front of the alternator. I
undid it. Once again not sure if I needed to but it was a small thing to undo.
b. Undo the two external torx bolts. They are long. Remove them.
c. Lever the alternator out of its bracket keeping in mind that it still has electrical
cables to the back.
d. Once the alternator is out of its bracket, it is time to remove the electrical
connections. I had a friend hold the alternator and I got under the vehicle. He held
the alternator so the back was facing me. I removed the nuts on the back-one quite
small (secured 1 wire) and the larger nut secured two wires.
e. Lift alternator out of vehicle.
5. Installation of new unit is reversal of the above instructions.
I missed anything or if it can be done more efficiently, place add to this DIY. Hopefully this will be helpful to someone in the future.
Also as a note, my BAS light was on after I completed this job and restarted the vehicle. I turned the steering wheel from lock to lock to reset the sensor.
Last edited by Michael Pillay; 02-18-2014 at 04:12 PM.