All done. Back up and working great! Here is a summary for anyone else having the same problem. Firstly, I have to emphasize I am NOT a mechanic, but do like using tools and enjoy the satisfaction of doing repairs myself. So here's my story of replacing an Alternator in a 2002 C240.

1. I got a Malfunction message that the voltage/alternator was malfunctioning. I suspected a weak battery or dead alternator.

2. I hooked up a voltmeter to the battery while the car was turned off. It read 11.75. Then I turned on the engine and took another reading with the voltmeter. The voltage dropped and continued to drop and I started to get all kinds of Malfunction messages. I concluded that since the voltage didn't go up to 14 with the engine running, and the fact that in actually dropped and continued to drop, that the alternator was dead.

3. So I decided to repair the alternator. I first disconnected the battery and began to charge it.

4. Next, I took of the belt. I couldn't figure out how to release the tension pulley (the pulley to the right of the largest pulley). Later found out that there is a "nut" like piece that you can put a rachet onto an pull up. Anyways, I lifted the tensioner pulley up and released the belt.

5. I disconnected two of the radiator hose clips that were close to the alternator. (This allowed me sufficient play to move the hoses to give me enough room to pull the alternator up and forward to remove it from the engine compartment.)

6. I unscrewed the two retaining bolts with a torx head. Then I gentley pryed the alternator loose. It was in the bracket pretty tight, but I used a screwdriver to shear it sideways to loosen it.

7. I undid the harness. There are two harnesses in the back of the alternator. One releases by compressing the harness clip, the other big one releases when you remove the Mercedes rubber cap and the unscrew the nut.

8. I then took the alternator out by lifting it and turning it and taking forward.

9. I took it to the shop where they bench tested it and then redid the voltage regulator, brushes and some other stuff? (I actually don't know what he did, but he fixed it and it looked and tested as new. Costed me $225 CAD)

10. I then put it back in using the exact same steps but in reverse.

11. Back up running!


So, for my first time (and hopfully last time), it took me approximately 6 hours. Most of my time was wasted figuring out which pulley was the tensioner, how to release the tension, and how to remove the alternator as it was siezed to the bracket. I could probably do it in 90 minutes or less now that I've done it once.

Good luck to anyone who has to do the same thing. Like I said, I'm not a mechanic but would say this is definitely a DIY job!

Brad.

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Dr. Brad

2003 C320 4Matic Station Wagon
2002 C240 Elegance
1982 380 SEL Star Certified