2000 Windstar Alternator Problem

First, I'm using a little LED cigarette lighter voltage tester.

When I cold start, voltage is 14.5 which is typical.

After 10-15 minutes, voltage gets around 13 volts and then acts like there is no regulation and limited amperage output. If I turn on accessories, the voltage decreases.

If I try pretty hard, the voltage gets down near 12v.

There are also indications of the voltage "fliuttering" about like there is a loose connection.

One question in particular: I've read that some models have the ECU control the alternator - not a voltage regulator. This really scares me since a charging problem could be an ECU problem.
A CLUE: This used to be my daily driver. I got a little car and now rarely drive the Windstar. It is parked on grass and I can tell it is getting beaten up pretty good from ground moisture. These problems did not start until after about a years worth of this limited use. I'm also convinced this inactivity caused the struts to go bad too.
Any ideas?

Thanks
Tom

If I had to guess, I'd say that one of the diodes is "winking out" so that the alternator can only produce 20-30 amps?

Just guessing.

If I knew the alternator had an internal regulator and NOT controlled by the ECU, I'd consider simply replacing it. But if it is a bad ground or connector in the control circuit, that is another matter.

The alternator has its own internal regulator. And AutoZone can do a pretty good bench test on the alternator ... depends on the skill of the test-person, of course.

If Advance Auto is not too far when you leave AutoZone, I would pay then a visit also and have them do another bench test. A second opinion never hurts, especially if the guys at AutoZone are not good at testing.

What bothers me is that the alternator behaves like I would expect (14.4 volts) no matter what the load.

I've done some more driving and as I drive, the voltage slowly drops to even below 13v.

I know old fashioned voltage regulators were set to a fixed voltage, however, I don't know if VR is designed to taper off to a "trickle charge" as the battery becomes fully charged. (I know for a fact that if you keep 14.4v on a battery continuously, it will become overcharged.)

QUESTION: Is the VR Old School and show show 14.4 volts no matter what load or how long engine has been running?

I replaced the alternator in my 2000 SEL this year and experienced something similar. It was strange because I didn't know the alternator was bad until my 3 yr old battery went dead.

I did learn that I had </=12 volts with new battery and 14.2 with a new alternator, then it slowly dropped like yours into the 12-13 volt range.

Bottom line: the Windstars of at least that year have something call "smart charging" that provides alternator output only when it's needed. I have not had charging system problems since then, so no worries. I thought it was strange that the dash light did not illuminate, but maybe it did not meet a specified threshold.