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Battery charge warning light on; but, she be fine?

1992 Ford Taurus SW 3.0L V6.

At first, the battery charge warning light would flash, sometimes, during driving. Now, the light stays on, solidly, with engine running.

The alternator has five wires: a three-wire connector; a one-wire connector; and the power wire (held by a nut).

I can’t find a five-wire alternator wiring diagram at Alldata, nor ARRC, nor in the Haynes Repair Manual. Nope, don’t have access to the FSM. I would like to see the five wire diagram TO the alternator, and the INTERNAL alternator wiring diagram. Where and how?

Tests performed:

Battery voltage: 12.6+ volts.

Voltage with engine running: 14+ volts.

Voltage with engine rpm varied: stable.



With the engine off, ignition switch on (run), the battery warning light stays ON (normal). With the three-wire connector disconnected from the alternator, the battery warning light goes off. Thus, there isn’t a short to ground between the battery warning light and the alternator connector.

Q: What is the solution to finding the cause of the battery warning light, and how to fix it? A piece of black tape stratigically placed?



Years ago Mavericks and comets had this sympton and it was caused by winter salt acumulation in the altenator. Used to hose out with clean water and blow dry with air. worked every time.

How old is your battery? Clean and check all connections also.

Here is an interesting link to some diagrams.

This one here may be similar to yours.

http://www.fordmuscle.com/pictures/Galaxie_406/3Ginstall.jpg

Alternators have 3 large diodes to rectify the 3 phase A/C output to DC…If one of those diodes goes bad, the alternator will still have some output (as your volt-meter points out) but there will now be some A/C ripple in the output also. This may be triggering your warning light.

An alternator test, available free at most parts stores, will spot the A/C ripple if it’s there…Sometimes you can hear the A/C buzz in your car radio when it’s in the AM mode…

I would like to know the amps, a so/so way of making a WAG is see if that 14+ is maintained with as much electrical load as possible (no don’t throw a wrench across the terminals)You want flawless operation of that light, many people dismiss the alternator light, but it is crirical in the charging circuit, if it is not working properly something is surely up.

Make that a pair of 3 diodes, in fact some alternators have the 6 for rectification and then what is know as a “diode trio” that is used to rectify current from the stator so that it can be used to create the magnetic field in the field coil of the rotor, the use of a diode trio cuts down on wiring. But still the actual alternator used six diodes.

Further digging at alldata-online yielded the alternator internal and external diagram. The alternator warning light (“battery light”) is turned OFF when the voltage from the stator reaches a certain value which is sent to the internal voltage regulator. For that voltage signal to get from the stator to the voltage regulator, it leaves the stator terminal, loops out into wiring bundle (why?), and back to the internal voltage regulator terminal.
The voltage may not be getting from one S terminal, through the loop, and to the other S terminal. That would prevent the “battery light” from turning off. I don’t have the car, to find out. So, I have a possible solution without application possible.
Thanks for your thoughts on this.

You have a wire coming from the alternator that sends a signal to shut off the charge indicator light on your dash. It might be a light green and red wire. If you can get to it, tug gently on it. I’ve came across them where they are open right where the alternator harneess ties into the main engine compartment harness.

I’ve had this same problem with my '01 Taurus. Took it to mechanic who tested the charging system (alternator, et al)and could find no reason for it. Been driving it that way for about 2 years now, South Dakota winters and all with no problems. The only thing worries me is if it DOES finally go bad I won’t know until it’s too late!