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post #1 of 3 (permalink) Old 12-01-06, 07:21 AM Thread Starter
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Bad Alternator/Voltage Regulator?

'97 Taurus GL, 3.0L V6 VIN U, 132K miles.

Recently noticed my headlights and dash lights occasionally flicker. At cruise speed they are somewhat dim and brighten up during mild acceleration. If you accelerate hard and bring RPM above 3500 the battery light comes on. Of course that could be just a worn tensioner.

My suspicion is alternator/voltage regulator.

1. What do you think?
2. What is the voltage with headlights on (or other accessories: blower, defroster) for this model? 14.7?
3. Can the voltage regulator be replaced? If so, is it the black module on the side of the alternator? Finally, is it worth it, or should I just go for the whole alternator given a price difference of about $50 ($110 for reman alternator; $60 for voltage regulator).

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post #2 of 3 (permalink) Old 12-03-06, 07:42 AM
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Re: Bad Alternator/Voltage Regulator?

4 things I would check: 1)Remove Alt and have it "load" checked at your local part store. 14.7V dont mean nothing if it dont have the Amp output to supply the power to the load. 2) Have a "load check" done on the battery 3) Battery Cables, I have seen battery cables corode inside the insulation the full length of the cable and that could be the culprit. 4) Check your ground's, Batt to engine, body to frame ect..

As for the Alt, replace the whole part if it checks out bad that way you know what you got.
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post #3 of 3 (permalink) Old 12-04-06, 06:11 AM Thread Starter
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Re: Bad Alternator/Voltage Regulator?

Thanks jwko.

As a quick update I checked my voltage yesterday and noticed something. At idle I'm running 14.1V with lights and blower motor on. When I run the RPMs up to around 3K I noticed a voltage drop off around 2K band. It took me a while to pin down the exact speed but it seems around 2K where the voltage drops off. Once I found the correct speed I watched it exponentially drop off to about 11V before I got too scared to continue.

On the road the band is a little different undoubtedly due to load. But there is still a narrow RPM band within which volts drop off.

I also popped off the S belt and checked noise and play in the alternator. It could be just normal wear, but I think there is some noise and slop in the bearings.

With 132K this alternator doesn't owe me much, so I'm gonna just replace the whole thing. If it turns out the voltage regulator isn't the problem, they get sticky about returning electrical parts, and I'll have to eat the cost.

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