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Discussion Starter #1
Hi - Having some issues with what I think is the alternator. I noticed a few weeks ago that an odd noise began to come from under the hood. To me, it sounds like a grinding noise but its loud and it has got progressively worse.

I'm also seeing fluctuations in the voltmeter. I got a check gauge light, and it was overcharging. I've had this problem before and it was a sign that the alternator was on its way out. I took the alternator out and had it tested, but it tested OK. I spin it on the table and it spins freely with no noise. But I swear it was making that loud noise while it was being tested.

I took it out again today, took it apart and found a thin piece of metal had broken that goes around the rear bearing. I removed it and put it back together. Put it back in and drove it...still makes the noise, can even hear it inside the car over the engine going down the road. I watched the voltmeter and it stays in the normal range so long as you keep the revs up...stop and the volts go way down and the car seems like it wants to die. But get going again and its fine.

Is this a symptom of a bad bearing, like its trying to seize but is OK if its going fast enough? If so, why don't I hear something when I spin it on a bench?

I also see that overcharging indicates a bad power/logic module. But in my experience, its these alternators that are junk and cause these problems.

I replaced the alternator in October of last year...I know because I asked some questions about my problem back then. Time to find a new alternator and forget these rebuilt AutoZone things. Any suggestions on where to get a new one? Any aftermarket ones that hook up with little or no modification? This is the external fan type with black back piece 90 amp...is there another alternator I can swap in from a Chrysler that would work too?
 

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Virginia Gentleman
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I'd say you have a bad alternator. You should have a steady 14.0-14.4 volts at idle (voltmeter should be a hair to the right of the middle mark on the gauge). I don't know that you can actually find a "new" alternator. Probably only remanufactured units are available. AutoZone doesn't seem to have the best parts.

We R&R the alternator in my son's car ('97 Mercury Tracer LS) 4 months ago with a reman from Advance Auto. No problems to date. Once I figured out to reinstall the belt, it was pretty easy to install. Should hook up with out any modifications. On his there were 2 or 3 wire connections and they were pretty much self explanatory.

You probably don't hear the bad bearing spinning it on the bench as there isn't any "load" on the bearing so it spins freely.
 

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Discussion Starter #3
Thanks.

Got another alternator and put it in. I started it up and let it idle. It started out fine, right where it should be on the voltmeter. Then as the car warmed up, the voltage kept going down. First 12.2V, then 12.0 and then under 12V...I think it bottomed out at about 10.5V or something. Finally 4 bars show on the gauge and when I started the AC, it dropped to three and the Power Loss came on. What's up with that?

I checked the voltage across the field terminals and got 8.5V or so...no lights, interior fan was on part way but no radio. Not sure what that is supposed to be. Alternator voltage matched the battery.

To test the voltage regulator idea, I put in a remanufactured Power Module. Same issue. Then I put in the remanufactured Logic Module and the car will crank but won't start. I can't get codes via the Power Loss light. So put the old one back in and it starts, but the charging problem is still there.
 

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Virginia Gentleman
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Obviously something is not right. The battery voltage should measure between 13.8 volts - 14.4 volts with the engine running at idle, around 12.6-12.8 with the engine off. What are you measuring the voltage with? The dash gauge is not all that accurate. Best to measure it with a multimeter if you have one.

At the very least you need to check and clean all battery, alternator and ground connections. Just a slight bit of corrosion can inhibit flow and give improper readings. How old is the battery?

I just went through some thing similar with my Ram. I noticed the gauge was giving me some odd voltage readings. Ended up replacing the battery and everything seems to be back to normal. The original battery was 7 years old. Will confirm after a few more days of driving. I had readings of 14.4 volts (engine idling w/lights on, fan on, radio on) and 13.8 volts w/engine off. The 14.4 was fine, but the 13.8 was high for a battery at rest - some of that was attributed to surface charge since I took the measurement right after shutting the engine off. A few hours later it read 12.5-12.6 volts.
 

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Discussion Starter #5
I checked it with a multimeter, scaling using the bars from the digital gauge seem to indicate that the gauge is matching the multimeter readings pretty closely.

I agree, something isn't right. The battery isn't that old (a year or so) and this issue probably hasn't done the poor battery any good either.

I've never had much luck with grounds...the ones I see seem to be tight and clean to me.
 

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Where did you get that alternator? It sounds like it's defective to me, like the brushes aren't contacting the armature. I'd start with that, if it were mine.
 

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If it starts out OK and falls as time goes by, it's not a ground. It's a diode in the alternator that's shorted, and it self-heats from the short circuit and becomes more 'leaky' as it gets hotter. Replace the alternator, or if possible these days, the diodes (I'd do the whole alternator).
 
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