Alternator, Battery Drain, Smart Charge

I am posting my solution to a common problem that has plagued many here for my grandson's 1999 Windstar. This was originally posted under a thread involving the REM (a missed diagnosis by shop #1).

The original problem seemed to be an alternator failure. After replacing the alternator twice, the battery twice and involving 2 "professional" repair shops, the symptoms ranged from a BAT light fading in/out, failure to start the car even after it had just been running. A voltmeter across the battery while engine running would start off near 14v and immediately lose ground as the engine warmed up. Eventually the voltage across the battery would get as low as 10.9v. At that point, after cutting the engine off, there did not appear to be enough charge left in the battery to spin the starter.

I am not going to post all the gory details, but I am sure it was not a lose or corroded connection as well as any wiring short or open, bad sensor input etc.

End the end, I decided to replace the starter motor, only because even a reasonably but not fully charged battery could not spin it and I viewed that as a separate problem.

It was a serendipitous decision because this also solved the charging issue with the alternator. Voltage across the battery starts off at 14.5v cold engine and drops to a nominal baseline of 14.2v at warm idle.

After driving with full load (max A/C, headlights, etc.) the alternator output gets as low as 13.8v but tends to stay around 14v which is well within the expected range.

I suspect there was some parasitic load through the starter motor or motor solenoid in the STAR/RUN key position that was not detected.

So for those of you that have searched the forums, internet, etc. looking for a solution to similar problems without success, do not discount the starter motor.

Thanks much! You really did the leg work on this! Now that you have discovered the starter, it's like ... "Of course!, it all makes sense!"

The new (remanufactured) starter motor came with a pigtail on the positive lead. The instructions recommended cutting off the original (Ford) spade terminal and crimping the new pigtail on the existing wire because of corrosion problems with the original termination.

The starter motor that I replaced could have been perfectly fine and the parasitic leak may have been completely external to the motor. A good clean up of the terminals may have been all that was required. But after all the difficulties with this vehicle and the short time line before my grandson starts back to school, I was in a "replace with new" mode.

I'm pretty sure starter-motors are programed to fail when; ...its raining, at night, when you are far from home, etc.,etc. So best to get it replaced. (I'm still on my original starter-motor @ 382K miles ... not smart!)