Wierd Charging Problem - Voltage regulator?

[MattBelliveau]

New prob.

When I left for work today, I noticed that my brake and fuel low idicator wouldn't turn off. This is usually true when I first start the car, but goes away as soon as I hit the accelorator. Now, throughout the day, I've started it a few times, and a couple of the times, it sounded like it wasn't getting enough power, but it started OK. On the way home, my stereo started acting like it wasn't getting enough voltage (turn on, turn, off, turn on, etc.). By the time I was about 5 mins from home, I had almost no headlights, windows barely worked, etc. I imagine I wasn't charging for about 20 mins. As I was getting off the highway, everything became normal. Then, three minutes later, I was going dead again. Everything appears to be there (belts, alt. etc.) Does this sound like it might be a voltage regulator problem? Is it possible to test one of these? Thanks!

[JimSmith]

Sounds like the brushes on the alternator are failing. When you change them you can either buy the assembly with the brushes mounted on the new voltage regulator, or you can do it for less money by finding the right brushes and installing them in the old voltage regulator. Instructions are available for each path by doing a search on the subject of alternator brush, or voltage regulator, replacement. In general they are all the same, but access is different for different models. Check FastLane for the voltage regulator if you elect to go that way. Good luck and I hope this helps,

Jim

[Perkinsguy]

A brush-regulator change may be the esiest thing you can do on your MB.....two screws and it's out, two screws and it's in! That easy!

If you are on the second, or third, change out, I would look at the armature for wear.

[MattBelliveau]

So, if I change out the brushes and the regulator, would that be the same as getting a rebuilt one? Is there anything else, in the alternotor, that could be replaced? Anyone know the part number or supplier for the brushes? Thanks!

[dannym]

Matt, this is what you want:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1Y70MFKNH1YM0LS2RF&year=1983&make=MB&model=300-DT-001&category=F&part=Voltage+Regulator

AS you can see it's only held in by 2 screws. Super easy to replace.

There are diodes and such in the alternator which cannot be replaced. If they go bad it replacement time.
Sd blue just wrote a testing procedure a few posts back.

Danny

[SD Blue]

Use a meter.

1)With a meter across the terminals, while running, you should be getting close to +14 VDC.

2)Then switch to VAC and you should be at less that 1 VAC.


If both #1 & #2 are not true, then the rectifying diodes are gone and the alternator needs replacement.

If only #1 is not true, then replace just the regulator.

Before doing any replacement, be sure and check all of your battery and alternator connections including the terminal strip. Also, the Batt-Chassis & Chassis-Eng. ground straps.

[JimSmith]

The easiest way to get the right part is for you to order through FastLane, by clicking on the "Buy Parts" button at the top of the page and using the drop down menus to find your car by year, make and model, then navigate to the electrical category and find the voltage regulator. Or you can call Phil at the phone number given on the page you get after clicking the button "Buy Parts" and he will do it for you over the phone.

The brushes are an integral part of the voltage regulator unless you are a particularly frugal, and capable, do it yourself type. Tracking down the correct brushes is a lot more of a chore than ordering the whole regulator, but it is also much cheaper - by memory on the order of $3-4 for the brushes and up to $80 for the regulator.

The alternator should be fine, but if you examine the brushes when you take out the voltage regulator and find them heavily scored and of substantially different lengths, there is an indication of a problem. In that case, I would buy another alternator, complete, also from FastLane. If you are a member of the Mercedes Benz Club of America, you may have a dealer who will offer a significant discount on such parts - in that case the dealer may be competitive.

Good luck and I hope this helps. Don't forget to do a search of the archives here, as there is much written about this issue that you should find helpful. The search function is a tab in the medium blue horizontal border just above the window with this text in it. Jim

[JimSmith]

Originally Posted by SD Blue

Use a meter.

1)With a meter across the terminals, while running, you should be getting close to +14 VDC.

2)Then switch to VAC and you should be at less that 1 VAC.


If both #1 & #2 are true, then the rectifying diodes are gone and the alternator needs replacement.

If only #1 is true, then replace just the regulator.

Before doing any replacement, be sure and check all of your battery and alternator connections including the terminal strip. Also, the Batt-Chassis & Chassis-Eng. ground straps.

Is there a typo here? If #1 is true, the voltage regulator should be fine.

If #1 and #2 are true, meaning those are the readings he gets, then the rest should be fine too? Why would meeting the criteria you set be grounds for replacing hardware?

Also, if the brushes are only contacting intermittently, there may be some peculiar readings that could make interpreting the results a bit less than precise. Jim

[SD Blue]

Yes, definitely a typo! There should be a not in both of those statements!

Thanks, Jim I will edit.

[MattBelliveau]

I really appreciate you help, guys!

[MattBelliveau]

Originally Posted by JimSmith

The easiest way to get the right part is for you to order through FastLane, by clicking on the "Buy Parts" button at the top of the page and using the drop down menus to find your car by year, make and model, then navigate to the electrical category and find the voltage regulator. Or you can call Phil at the phone number given on the page you get after clicking the button "Buy Parts" and he will do it for you over the phone.

The brushes are an integral part of the voltage regulator unless you are a particularly frugal, and capable, do it yourself type. Tracking down the correct brushes is a lot more of a chore than ordering the whole regulator, but it is also much cheaper - by memory on the order of $3-4 for the brushes and up to $80 for the regulator.

The alternator should be fine, but if you examine the brushes when you take out the voltage regulator and find them heavily scored and of substantially different lengths, there is an indication of a problem. In that case, I would buy another alternator, complete, also from FastLane. If you are a member of the Mercedes Benz Club of America, you may have a dealer who will offer a significant discount on such parts - in that case the dealer may be competitive.

Good luck and I hope this helps. Don't forget to do a search of the archives here, as there is much written about this issue that you should find helpful. The search function is a tab in the medium blue horizontal border just above the window with this text in it. Jim

So, when I buy the regulator, the new brushes come with it?

[ImBroke]

Yep, brushes come attached. I just did this yesterday.