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Most modern alternators unless of the smart-charging type have just two connections and perhaps a thick ground bonding cable if the machine is rubber mounted.
I suggest you check those connections and ensure the thick cable is in good order and providing a good current path to the battery and the other wire (which is the earthy side of the ignition light) is not shorting to ground which would cause the battery light to remain lit. Disconnecting the wire should put the light out.
If this is your type of alternator and all is ok with the wiring the alternator must be faulty.
If there is more connections than just two it is possibly an older machine sensed alternator that can have another one, two or three wires or if there are several additional wires, especially in a separate multiplug, it could be a smart-charging system where the alternator is fairly conventional but there is influence from the engine management via another small ECU which also controls the battery light.
During periods of acceleration the system prevents the alternator from charging to free extra power from the engine. If there is a fault in the smart-charge system disconnecting the additional multiplug will allow the alternator to charge normally until the system can be repaired.
Unless there is a smart charging system fitted to your car the alternator wiring is simple and straightforward.
A defective smart charging system can stop the alternator charging and the presence of one of those idiotic things is recognised by there being in addition to the usual thick battery wire and thin wire from the battery or ignition light there will be a multiway plug with a few additional wires.
If it has one of those, disconnecting it and rechecking the charge rate will see a normal output restored if the alternator is healthy but the smart charge is faulty.
With both types the main wiring should be checked before condemning the alternator and if it is mounted in rubber bushes there will also be a fairly thick ground wire.
If all is well with the wires and connections the alternator must be faulty and if it was a new or reconditioned unit as it is only a few months old replacement should be completely free.
The belt could be slipping. Is the thick red wire hooked up at the alternator it should run from the alternator to the battery. Check voltage at the stud where the thick wire comes off the alternator if its not reading high 13's or low 14 volts your alternator is bad. I've gotten multiple brand new rebuilt alternators that were bad from the get go.
An alternator can run on two wires, the thick wire is the supply to charge the battery, direct to positive, via fuse box or starter supply. The thin wire possibly blue on Fords, is the energiser wire from the dash charge light, without this connected the alternator will not charge. If on the new pigtail two wires are thick (30amp) you can ignore one, some vehicles double up on the charge supply wire.
Check:
- Battery (Specific Gravity and cells test)
- Alternator.
- Starter.
- Battery to starter motor wire (thick white in color).
- Battery to alternator wire (thick white in color).
- ECM ground wires attached at engine.
- TDC sensor.
Well, according to my diagrams for 88-94 models, the alternator only uses the red and brown. There are pink-black wires that power some of the sensors and solenoids but should go to a fuse marked ECM in the fuse box. Have you tried hooking up the harness without using the pink-black wire ?
Check alternator voltage, in back of alternator, on the thick wire that is bolted to the stud, with engine running should have no less then 13 volts, if you do, then we know for sure alternator is good, check for bad fuse link at starter solenoid, depending which one you have, on starter on on the fender on passenger side, fuse links most of the time will have a small tab on the wire it self, pull gently on wire if it feels like a rubber band, bad fuse link, also if you can't find it, you could also run a new wire (thick 6 gaug) from alternator to battery.
It sounds like you have answered your own question here...? the thick wire from the alternator connecting to the starter terminal feeds electricity back to the battery though the starter cable when you are running... if you have a manual you can see for yourself in the wiring charts. Hope this helps...
located the wire coming from batterie light thats very easy you just have to aply groun to one of the 2 wire conector and the alternator light will come on with ignition on, be carrefull the other will have 12 volts, then the big and thick wire goes to the big post on the alternator, and the batterie light wire goes to the remainig small alternator wire, i belive must to be brown color
on alternator but can't remeber, good luck
It be goeth tooith the battery (+) terminal!!!!
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