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Old 11-18-2007, 05:39 PM
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Strange alternator problem

I have a rather odd problem, odd to me anyway, with my 98 Ranger alternator. The darn thing is charging just fine at idle and will increase the charging rate as engine speed goes up just like it should however at between 1500 and 2000 RPM it will suddenly quit charging. I have both a voltmeter and a warning light and the volt meter will drop from about 14 volts to 12.5 and even less if the headlights are on and the warning light also comes on. But then when I let the engine speed fall to around 1500 RPM the light goes out and it starts charging again. What could possibly cause something like this? At this point the only thing I have checked is the belt and it definitely is not slipping and I am suspecting the voltage regulator but to be honest this is really just a guess.

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Old 11-18-2007, 06:16 PM
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never heard of this specific problem , but I had a 79F-100 that wouldn't charge unless the lights were on ! It ended up being the regulator , but at least they're easy to change!
good luck with it!
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Old 11-18-2007, 06:38 PM
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Get a bowtie that will fix it.LOL
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Old 11-18-2007, 11:25 PM
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I just looked at autozone, and they claim that the 98's have the voltage regulator in the alternator. They don't offer any service kits for the regulator.

It does sound like the regulator. In general, I could see that the regulator could failat a higher voltage in -- that's what your alternattor is putting out at higher rpm. I can't see how the alternator itself could fail in this way.

Possibly someplace like Rock Auto has a replacement regulator. Otherwise I think that you're out a new alternator.

BTW have you tried this with the hood open ( parked!) to make sure that the
belt isn't slipping?

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Old 11-19-2007, 07:48 AM
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Ok, I got out there early this morning and removed the alternator and when I took out the regulator the problem became apparent. One brush looks good and has only moderate wear the other one however is simply gone, nothing but the badly burned end of the spring running against the armature with predictable results. Guess I will just put it back together and run down to AZ and exchange it.
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