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  #1  
Old 02-22-2005, 02:14 PM
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Alternator light??? '87 300d

Morning!!! By the number of people here, doesn't anyone on this board work? Or is everyone like me and scan it throughout the day?

Driving in to work this morning and the red warning light with the battery outline on it came on. Slowly at first but within a mile, it was steady red.
Anyone know what this is trying to tell me, just do some maintenance on the battery and cables or is this pointing to the alternator itself?
I figure to limp home this afternoon and clean up the battery but am looking for other items to look for.
And I guess that as long as I can get her started that unlike a gas engine it should continue to run until I shut it off?
Thanks for any input,
Glen

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  #2  
Old 02-22-2005, 02:58 PM
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morning red eye.

Not many of us work as we are mostly all independently wealthy. Why would we want to go out there and catch the morning red eye? Actually sounds like your alternator decided not to get up this morning as well. But anyways you could remove, check, and clean the various connections to your alternator to insure they are okay. Think your car has a serpentine belt but make sure the belt is still tensioned properly whatever type it is. Guess you could order a 20.00 voltage regulator and try it.(I would) If above does not correct the problem likely 90 percent chance it's in the alternator itself unfortunatly.
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  #3  
Old 02-22-2005, 03:03 PM
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Iceman,

Probably not the alternator brushes which is usually the problem. I say this because the light doesn come on when the brushes wear out. Kind of a stupid design because usually worn out brushes are the first thing to cause the alternator not to work.

P E H
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Old 02-22-2005, 03:28 PM
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Help from the independently wealth.....

I could almost believe this.....99.9% of the people here seem to the the most tight fisted of all the individuals I know of. Save your money rather then spend it on new vehicles!!!

So it sounds like time to start with the battery and move to the altenator. I did stop and check to see that the serpentine belt hadn't broke and everything looks good.

Thanks,
Glen
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  #5  
Old 02-22-2005, 03:38 PM
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Everytime I have had the dreaded red light it turns out a diode in alternator has gone south. How old is the battery? If the battery is weak it can put more stain on the alternator causing a blown diode. The vibration from a diesel can also cause a coil winding to fatique and come loose. One of the McParts stores can test it for you.
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  #6  
Old 02-22-2005, 03:55 PM
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newer battery, older altenator

It's a fairly new battery, at most a couple of years old. Never have problems starting, even on the cold days.
I guess like always, hope for the best, plan for the worse......

Glen
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  #7  
Old 02-22-2005, 05:08 PM
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I say check the brushes, the regulator is easy enough to take out. Just 2 screws hold it in. If the brushes are short try pulling on them gently to see if you can get a little more length out of them. Put the reg back in and if the lite is out order a regulator.
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  #8  
Old 02-22-2005, 05:25 PM
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In my recent case of worn alternator brushes, the red battery light did come on. For the most part it would be brightly lit right after I started, and tend to dim out somewhat going along. Sometimes when hitting a bump it might go out completely or brighten again.

Ultimately, the light went away completely. Not good - at this point you don't have enough battery juice to drive the light circuit.

My recommendation for the cheapest and most likely technical fix is a replacement brush/voltage regulator assembly. You can remove the old one and if the brushes are pretty short then its about time for a replacement.

Ken300D
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  #9  
Old 02-22-2005, 07:30 PM
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Ken300D,

I'd say the most economical way is to replace only the brushes if that is what is wrong. I replaced mine about 14 years and 140,000 miles ago and the alternator has been working fine ever since. But its probably due for a new set of brushes soon at 263,000 miles but not due for a new alternator.

P E H

Last edited by P.E.Haiges; 02-23-2005 at 03:19 PM.
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  #10  
Old 02-23-2005, 12:54 PM
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I would do that too if I had a good source of the brushes and spent some time determining how to take apart the voltage regulator assembly. Many of the old diesels out there are at the mileage where the brushes are about gone - so I bet there's a lot of unnecessary alternator purchases that take place when only the brushes are needed.

I found it interesting that the alternator on my 1987 300D uses the same voltage regulator assembly as the older cars, at least the 1982 and 1984 cars. Makes keeping spares easier - if only they used the same oil filter.

Ken300D
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  #11  
Old 02-23-2005, 02:59 PM
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After a closer look

Hi,
And thanks for the input.....
I pulled the battery and cleaned it when I got home last night. Put the charger on it and found the battery fully charged. Put it back in the car and check voltage, had 12.65, with the car started voltage dropped to 12.30. Looks like it is not charging at idle, but it must be at higher rpm's.
We listened closely and seem to hear some noise from the alternator itself. Due to the age of the car and mileage, 251,000, I'm thinking of changing out the alternator, it does appear to be the original.
Glen

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