When I have the climate control on the blower motor speeds up when I start moving, and slows down again when I come to a stop. I have noticed the dash lights dim a little when the cars isn't moving and brighten when the rpms go up. The battery was replaced last spring. Sound like an alternator? Or are they any other things it could be.

Thanks
Andrew

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Check the belts and the voltage regulator on the alternator. If the brushes are worn, you should just replace it. It's fairly cheap and easy.

I just went through this on my '80 300SD. Replaced both and I'm up and running again.

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1979 300SD
1975 240D

Has your dash light for the battery come on?
If not did you check the bulb to make sure it would work?

Loose grounds also can cause electrical problems but I agree it's probably your voltage regulator.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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The belts were replaced this fall, so they may have streched by now. I'll check that.

I believe the battery light works. It comes on when you put the key in and turn it to glow.

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You can check the voltage regulator for brush wear in five minutes. There are two screws on the back of the alternator that hold it in place. Pull it out and see if there is any brush length left. If there isn't get the cheap unit from Phil. I bought one a few years ago for $14 and it has worked fine. There's no need to spend a bunch more money.

Once you have a new VR pack in place if it is still doing it, use a DVM and do a voltage drop test between the negative battery post and the alternator case. It should read very near zero. Do another voltage drop test between the connector at the alternator and the positive post on the battery. If that one is more than .2V or so, your wiring and/or connections need attention.

Good luck,

Looks like it is the brushes on the voltage regulator. One is about 1/8" long and the other is 1/4". Can you replace just the brushes or do you have to replace the whole regulator?

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Just put a new regulator in. Then clean all the ground connections.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
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Call Phil and get one of the $14 regulators. They work great.

To answer your question though, my wife had a 73 250 back in the late seventies, early eighties. It was sort of an interim regulator before the integrated units like we have now. It had an electromechanical regulator on the firewall and a connector that fit in the place of the VR like we now know it. The brushes wore smack dab out and I went to get parts. They could not replace the original but wanted to sell me the integrated unit like we use now except it was over $100. And those were 1970's dollars during a day when I didn't have a lot of them.

So, I went to the auto supply store and told them I wanted to buy some alternator brushes. They asked what make and model and I just said off the top of my head "a 1970 Chevy." He went got them, I looked at them and paid him the $1 or so he wanted. I took them home and filed them down on one side and soldered them in place. It worked great and they were still in there many thousand miles later when she traded the car.

Now, for $14 I would not bother with makeshifting brushes and I would not have done it then either.

Call Phil and get a new regulator and you will be happy. Before doing it though reach down in there where you pulled the VR and feel of the grooves where the brushes ride. If they are deeper than about 1/8", replace the alternator.

Good luck,