Alternator Help Needed 87 300SDL
 

I was driving home today and had some very strange things start to happen with my electrical accessories. The Valentine One kept resetting itself, the radio started turning off and on, turn signals stopped working, and the windows were dead. I pulled it into the garage and tried to restart...totally dead.

The battery was my first suspect, as the battery was installed in 1997. The car ran fine, so I didn't really think the alternator was to blame.

I installed a new battery. The car fired right up and it seems to be operating normally...the power accessories are working fine. However, I noticed in the dark garage, the red battery light is lit ever so slightly. It doesn't change in intensity when a load is put on it.

I'm now thinking the alternator may be to blame. I've done some reading here and there has been mention of brush and/or regulator replacements rather than needing to replace the entire assembly.

If you think this may be the way to go, how would I go about obtaining the brushes and regulator? And how do they get installed once I pull the alternator?

I finally had my alternator go out on my 190 at about 300kmi. I did a little research and decided to purchase a rebuild. A rebuild is about $100 from Cano Electric on the north side of chicago (on western at about 3000 north as I recall).

I also purchased an alternator for my 617 123 from them as well. I have about 50kmi on the 190's new alternator and about 25kmi on the 123's. So far so good.

BTW, my 190 had the same symptoms and I did the same thing you did, I first purchased a new battery.

Lance,

The brush assembly fits into the back side of the alternator housing and includes the voltage regulator. There are some on the site that know how to change out the brushes themselves for a few bucks. I have taken the tact to change out the assembly. They used to be between $20 and $30, but I do not know what they go for now. At any rate, the job is relatively easy - you have to unplug the wire held in a socket by a little spring clip, then unscrew the two mounting screws on the "ears" of the flange that holds the assembly in place. Once the screws are out, you kind of roll it towards the centerline of the alternator to get it out.

Examine the unit and if you see the brushes, carbon sticks, are worn down under half an inch or so, they are shot. Examine the arc worn into the bottom of the brushes and look to see if it is smooth. They should be smooth and about the same length. If they have big grooves or are very uneven, there is a mechanical or electrical problem in the alternator. Changing the brushes will make the unit work again, but they will wear out relatively quickly and will likely not be charging your battery correctly.

If the brushes show signs of other problems in the alternator, try ordering a replacement from Fastlane. I think they have the voltage regulators too, but if you need one right away, try the dealer or an auto electric shop. Good luck and I hope this helps. Jim

FastLane has the volt.reg./brushes unit for approx. $15+ bucks. They probably have it for your model Benz. With overnight delivery, your ready to go. I carry a spare in my car. It's so cheap, I'd say it's worth a chance. Good Luck.

Thanks for the replies so far!

Another question I should probably ask is what is the best way to get the alternator out. Looks as if it will be relatively easy to remove from the bottom, but what should I look for?

I have the 126 service CDs, but they really aren't all that much help for this.

Lance,

I have not done the job on your model, but I have never taken an alternator out to replace the brushes. If you have access to the back side of the alternator it is relatively straightforward.

Taking the alternator out can be a chore due mainly to accessibility. Good luck, Jim

Okay, I ordered the regulator assembly from FastLane. Do you think this includes the brushes as well? It looks like it may from the pic.

Thanks again!

It should definitely include the brushes. Good luck, Jim

i changed mine today and it was about a 15 minute job, with the bumper stabbing me in the stomach that is

What do you guys think of upgrading the alternator size? This current 55A is puny. Would an 80 be ok? I see the local parts stores sell 80A that fit my car, or so their websites say. Or are there mercedes alternators that are bigger that can still fit in my car.

Lance:

Don't pull the alternator. Just slide under the car and bring a short flat screwdriver and a flashlight with you. 10 minute job max. I did mine at about 275,000 miles.
Good thing you replaced your 97' BATT. My experience is that the diesel's never give you notice. One day, all of a sudden, the Batt is just useless.


87 SDL 296,500

So you really think this can/should be done without removing the alternator...sounds fair to me.

I'll be giving this a shot probably this weekend. If there are any tips that can make the job easier, maybe let me know.

Thanks again for all the responses.

Problem has been resolved. The brush/regulator assy took all of 5 min to replace and all is fine.

Pretty good---5 min of time and less than $20 to get my car up and running correctly again!

Thanks for the advice.

Good to hear you got it fixed.

Next repair may be the electric cabin air fan that above the front passenger's feet. The electric blower motor's don't seem to make it to 300,000. More time involved than the voltage reg, but not too bad of a job. Carefull not to damage the expensive plastic fan portion of the unit.