1979 300td alt. light

alt light comes on for no reason, when I first got the car the light started coming on so replace old alt. good for about a week then it starts coming back on
now I don't know what to chase kelly......
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How about belt tension? A proper alternator should give around 14 (or even 14.5) volts at idle.
kjs300td wrote:

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Sounds like you didn't need to replace the alternator. I hope you kept the old one, since it's likely still good. Is it possible they installed another alternator, but put in the old, worn brushes? (Stranger things have happened) Check and tighten all electrical connections--battery posts, ground, etc. Maybe spray them with a contact cleaner, like Nutrol.
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