93 Taurus intermittent battery warning light

3.8 V6 sedan with about 160,000 miles. The battery light on the dashboard is coming on at seemingly random times, but with increasing frequency and duration.
Symptoms:
It (battery warning light) sometimes comes on in the day, with no headlights on. The RPM of the engine does not appear to make any difference. Motor runs well at all times. At night, headlights remain bright at idle. Starter turns engine over at normal speed and engine starts and runs well. Serpentine belt appears adequate and there is no squealing.
I am thinking that the generator and or the voltage regulator is the most likely cause. Of those two, I'd guess (and hope, since it is probably cheaper) it is the voltage regulator that attaches to the back of the generator.
Before I start replacing parts, any input from Taurus owners or mechanics regarding most likely cause would be much appreciated.
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Tony Sivori
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It sounds like a loose wire or connection. It could also be the alternator getting ready to die.
Jeff
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I had the same issue on my Taurus wagon. I found that the small plug at the top of the alternator was worn/loose. With some eyes on the dash, wiggle the plug. If you get blinking, you've got the same problem I had. Because I'm a cheap bastard, I found that a small wedge of some sort( I used a twig ), inserted beside the plug, will re-estabish a connection. I ran mine that way for years.
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On Sun, 19 Apr 2009 14:44:52 -0500, J Wald wrote:

Thank you, I will check that out.
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You didn't say how old your battery was. If more than 6 years, consider a replacement. (This is in addition to all the loose wire theories, etc.)
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On Sun, 19 Apr 2009 14:30:08 -0700, D. Stussy wrote:

I've had the car about three years. It had starter trouble when I first got it, and I think the previous owner had put in a new battery to try to fix the defective solenoid.
I took it to Autozone today. The light was not on when they tested it, but for what it's worth, they said the battery, alternator and voltage regulator all test good.
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wrote:

With worn brushes, when the light is off it WILL test good..
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On Sun, 19 Apr 2009 21:46:49 -0400, Tony Sivori

I suspect they tested in a conventional manner. Since you have already replaced the alternator, it may take a bit more comprehensive testing. I have had a couple of Ford alternators with a bad winding that only failed when warm enough. The last one was removed and tested 3 times on the bench and in the car twice before the rebuilder was able to see it in a failed condition. By the time he shut off the engine and hooked up his equipment, it was back to normal. The alternator was removed and placed into an oven to get it hot. It was immediately bench tested and found dead. When disassembled, the rotor was found to have an open winding when hot. Another rotor kept it going with no further problems for at least the next 5 years before I sold the car. I suspect your alternator would produce a far different scope trace pattern as it warms up. Autozone cannot do that. The only remaining choice with them is to replace the alternator with another which may be at your expense.
Lugnut
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On Mon, 20 Apr 2009 09:13:16 -0400, lugnut wrote:

I'm not sure how I managed to give you the mistaken impression that I replaced the alternator, I do tend to ramble on a bit. I haven't replaced the alternator.

I've heard of similar temperature sensitive failures from ignition coils.

That's the problem with intermittent failures. It will be a lot easier to know what's broke once it breaks and stays broken. But I hope to avoid that. Thanks for your help and observations.
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On Tue, 21 Apr 2009 08:38:10 -0400, Tony Sivori

Sorry. I've been "over the hill" for several decades now. My reading comprehension is not that good sometimes. Intermittent is the longest fout letter word in the dictionary when it comes to problem solving. Fixing a dead system is definitely easier then catching it on the fly.
Lugnut
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On Sun, 19 Apr 2009 15:07:38 -0400, Tony Sivori

At 160K, you are around the life end point for Ford alternators in my experience. It is usually a matter of brush wear when the alternator charges decently with the exception of an occasional light. The regulator and brushes are replaceable if you are handy. Otherwise, the fix is a new or rebuilt alternator.
That said, you should check the battery ground cable on the driver side of the radiator. They have a nasty habit of corroding where they split between the radiator and battery in the hardest place to put big hands. If that is the case, it will eventually get to the point that the starter turns the engine but, it will not start sounding like a failed timing chain. A new ground cable is the answer there.
Lugnut
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On Sun, 19 Apr 2009 17:35:39 -0400, lugnut wrote:

I replaced the radiator on it last October. So that ground wire was well visible. I don't recall seeing anything ugly. On the other hand, maybe I screwed it up putting in the new radiator. I'll have a look at it, if it ever stops raining here in Lousy, er, Louisville.
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Tony Sivori wrote:

You can get these cheap little three LED battery testers that plug into the cigarette lighter. Makes it easy to keep an eye on if its charging or not.
Make sure the grounds to the firewall and such are tight and not corroded.
Also, it might pay to take the serp belt off and check that the pulleys are not full of junk and clean. As well as check the tensioner. I think it takes a t45 or such to take it off.
bob
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wrote:

My suspiscion would be worn brushes.
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Same problem on the wife's 93...connector latch broken...a dollop of RTV solved the problem!
Steve

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