2002 C240 Alternator Replacement

[drbrad]

I recently got an error message about voltage and battery problems. I hooked up my voltmeter and it showed that the charge on the battery was 11.75 without the car running. Then I started the car and checked the voltage, (assuming that the voltage would increase if the alternator was functioning properly...), however, the voltage reading on the battery dropped and continued to drop. I assumed at this point that the problem was a faulty alternator.

I've decided to replace the alternator and battery. I've removed the belt, and loosened the bolts holding the alternator. The problem I'm having now is how to I remove the spacer sleeves? I understand that I have to remove these before I can take out the alternator and undo the wiring harness.

Thanks for any advice.

Brad.

[drbrad]

I'm really in a bind...I've pulled off the belt and unscrewed the two bolts that hold the alternator to the bracket, but I still can't remove the alterator. I've read that I have to now remove the spacers but don't know how.

Any help is appreciated!

Thanks.

[ILUVMILS]

Hmmmm........I've never had to remove the spacers to get the alternator out. You may need to carefully "help" it out with a suitable pry bar. I've done quite a few of them and never had a problem.

Also, you should be able to fix your charging system issue by replacing the voltage regulator. Unless you've got high mileage the alternator should be OK.

[drbrad]

Thanks ILUVMILS. I'll try to wedge it out tonight again. The vehicle only has 140K Kms, so I'll have the alternator bench tested before getting it rebuilt...any other suggestions on how to get this thing out is appreciated. BTW ILUVMILS, once I get it loosened from the bracket, which way is the best way to get it out of the engine compartment? Upward, forward or from under the car?

Thanks again!

[drbrad]

Ya...got the alternator off the bracket by prying it a little. I guess it was a little seized. Now to figure out how to take off the wiring harnesses. Any help here is needed. I have no clue on how to do this.

Do I just pull on the harness? which one is the harness? There is a little knob on the back of the alternator that has a small mercedes star on it. Does this loosen the harness some how? I'm stuck again!

[drbrad]

Ok, figured it out...the smaller harness is the typical clip, just compress and pull. The larger harness is held in place by a large nut that is covered by that little mercedes cap. I had to just pull on the rubber cap to get it off....almost there....

[drbrad]

I was able to get the alternator out of the engine compartment from the top. I just had to move two radiator hoses by unclipping them.

Just had the alternator bench tested and it showed charging at 10 volts. He told me it should be around 14 volts.

He'll have a look at the volt regulator and brushes.

He said he'll rebuild it for $225 CAD. I said ok. I guess that's the going rate?

So, I'll get it back and re-install it this weekend with a new battery. I'll be into it for around $400 for a thousand dollar job....it'll be about 6 hours of my time (not really worth it), but extremely satisfying to have done it myself (with some great advice), and learned a little on the way!

My next post will be a summary of what I learned for the next DIYer....

Brad.

[drbrad]

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.

[drbrad]

One last step that I just noticed. I continued to get an error message about the ESP not being available. I thought maybe it was due to a weak battery, so I checked that. It was fine. Then I searched the forums here and found that I had to reset the ESP by turning the wheels fully to the left, then fully to the right to reset the ESP. That cleared the error message and all if well....good luck to the next DIYer who has to replace their alternator in a 2002 C240....