i have an 82 300TD. Had a few times in the last month or so that I needed a jumpstart. The first time I put a new battery in. Was a while before it happened again. I guess its possible that you can go quite a while on a battery without the altnernator charging it (i.e. a full battery with one of these gets you quite a few times through the glow cycle and many miles of headlights before draining it completely?). After the second time the battery went dead I put in a new VR (well by "new" i mean I pulled one off my parts car...that was newer than the one on there). A few weeks later the battery went dead again. I got jumped. The jumper cables were only on for about 30 seconds and the car made it all the way home with the lights bright and the windshield wipers at full speed...which made me feel like it must be getting a charge from the alternator.

My understanding was that the alternators rarely go bad on these cars...that it was mostly the VR. what should I be checking to see where my problem lies? Thanks

Did you check the brushes on the replacement regulator to be sure they had plenty protruding from the housing?

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

The brushes are those two little sticks of graphite (or whatever it is)? The replacement one was off a car that had been charging and they were longer than the ones I replaced them with.

Remove the alternator and take it to AutoZone to have it bench tested. Other parts in the alternator such as diodes and brushes do fail. If the alternator checks out OK then you can look at wiring issues or even loose alternator belts. Make sure you have clean corrison free battery cables also. If you have a volt meter you can check the charge rate at the battery. Should be between 14-15 volts.

If they have Harbor Freight stores in your area make the about $6 investment and pick up a digital Volt/Ohm meter to help you trouble shoot.

Start with the basics.
Whey your fist turn the Key does the Battery Charging Warning Light come on? If not it could be that the bulb is out. Unfotunately you need that bulb working for the Alternator to charge. Also that bulb needs to be a 2 or some some souces say 3 watt bulb.

Once the engine is running that Battery Charging Light ought to go out.

If you don't have the Volt/Ohm meter if the do this where you are you could go to the Auto Parts store for a free charging test and they will tell you if you are charging or not. They should tell you what the voltage you are getting is.

Some of the reasons for poor charging can be that Electrical Connector that plugs into the Alternator can be corroded and that would keep the electricity for easily conducting.
Next is that Alternator needs to have a good ground. Lots of Alternators are terribly rusted in the area that they make contact with the Block and that can cause a poor ground.
Some people have have used a single Jumper Cable from the negative Battery Terminal to the frame providing another ground of the Alternator to see if the vlotage goes up indcating that the ground is bad. But you need the volt/ohm meter to tell.

Woulden't hurt to clean the contact areas of the Chassis to Engine Ground Cable and the Battery to Chassis ground cable.

__________________
84 300D, 82 Volvo 244Gl Diesel

at idle it charges at about 13.5v. with wipers and lights on it goes to 13V. was wondering if it was coincidence or not but its possible this problem is only happening on nights when its raining (lights and wipers on). maybe alternator can't keep up.

i'll look into corroded connections next. thanks for the help thus far.

13v is rather low. You should see 14-14.9 volts for a good charge.

Yes, it very well could be a connection issue. I put in a Battery with different termial locations and had to change the negative Battery Cable. After doing that I gained a whole volt. I cut back the insulation and found that the cable was corroded internally.

I started of with 13.7 Volts and ended up with 14.7 volts after the cable change.

__________________
84 300D, 82 Volvo 244Gl Diesel

well i went to investigate my VR and the wiring harness. the shortest point on the shortest brush was 5/16"...which I assume is getting low. additionally, the VR was installed with philips heads bolts...which is weird only because you can't actually fit a bit back there to unscrew one of them..you have to use vice grips. in any event, when i went to re-install it didn't feel like you can really get one of the bolts to tighten down all the way. its gets pretty damn tight...but still spins pretty freely.

also, i tried to take the wiring harness off to inspect it, but could't get it out. is that little wire clip supposed to come out completely...or do you just swing it off the back of the harness and let it hang down.

after messing with both those things it looks like i lost charge even more (getting only 12.5V at the battery now) so i'm assuming its one of those two things. i'll order a new VR just cause its cheap and easy.

can anyone tell me how to get that harness off completely so i can check it out?

thanks!

The spring hinges/pivots to one side.

I believe the minimum brush extension is 2mm.

One side of the voltage regulator needs to be pressed against the Alternator housing/frame and the contact area on the housing/frame has to be bare metal.

Inside of the Alternator there is a metal finger that makes contact with the Voltage Regulator and it also has to be clean enough to make good contact. The one in th pic is kind of corroded.

In both cases the Voltage Regulator has to be pushed in all the way and bolted tight.

Attached Thumbnails

   

__________________
84 300D, 82 Volvo 244Gl Diesel

How are you supposed to get the wiring harness off the back of the alternator?Im trying to check those connections but I can't get it free. Wire clip is loose and I have tried tugging lightly and even prying with a flathead...but I can't get it. I'm afraid I'm gonna break it. Im trying from below. Just making sure I'm not missing something..,

I have not read of anyone having that issue and it has not happend to me.
The Alternator in the pic is likely not the one you have bit it has a similar spring clip. In this case the Spring clip needs to be mofed in the diredtion of the arrown and it is going to end up where I drew the red lines. Note that you pivot the spring away from the wiring on the connector.

After that the Connector is suposed to pull straight out.

Just in case the Alternator in the picture is a Motorola Alternator and there is a few Mercedes that have them. But from what I have read on the forum more then 99% are going to have a Bosch Alternator.

So if you damaged our Alternator Connector pulling it out another Connector can be had at junk yards. Also places like Autozone sell new connectors (most european cars of around the same year or earlier used the same connector).
With both you would have to cut off the old Connector and splce in the other conntor.

Would it damage the make blade connectors in the alternator? That is unknown as you are the first one I have read of to post the stuck connector issue.

Attached Thumbnails

 

__________________
84 300D, 82 Volvo 244Gl Diesel