I thought the battery was fine this morning. After work, I barely got it started. I tried again, but it was too dead to turn over. I can jump start it, and it will go, but it will not charge the battery. The radio plays, but it turns off when I use the lights and foglights (or Hi-beams). The lights come on and work while running. Actually, they still looked pretty bright just now when I tried them without starting the car.

Does this sound like the voltage regulator, or alternator, or? Thanks for any help you could give.

It sounds like the alternator is not charging the battery.

It is possible that a replacement regulator with new brushes is all that will be required. Easy job, can be done with alternator on engine.

It is also possible that replacment slip-rings will be needed. Not as easy, requires removal of alternator.

Best Regards,
Jim

And then I refilled the battery with water. Sheesh.

Well, that will teach me to check first things first, I hope.

Put a voltmeter on the battery. Check the voltage with the engine off. Should be close to 12 V.

Start the engine. Run it up to 1200-1500 rpm or so.

Should be above 13.5V. If it is still near 12V, then the alternator or regulator requires rebuild and/or replacement.

83/300CD,

If the voltage doesn't goto 13.5v when engine is running 1500RPM, check the alternator brushes. If they are worn to about 1/4 inch, they probably need to be replaced.

You can replace the brushes only with out replacing the voltage regulator. All you have to do is solder the brushes in the regulator bracket and replace the bracket and regulator in the alternator. NOTE: You don't have to remove the alternator from the engine to R&R the voltage regulator.

I replaced just the brushes about 14 years and ~150,000 miles ago and they are still working fine.

P E H