1996 Ranger alternator tests prove it to be OK. Truck starts and runs; alternator puts out what appears to be excessive power (14.2 amps) to a nearly -fully-charged battery. The alternator charge warning light STAYS LIT ! 15 amp fuse in the PDB blows. Tried up to a 25 amp fuse, and it blows too.

ok all cars ran before we all know that ,what matters is only NOW and tomorrow.
the starter is dead that is the only real clue.
my sisters ranger had manual transmission does yours>?
dead or dim head lamps and wipers and blinkers dead. mean you just lost all 12vdc power, yes that hammer trick ive done for 50yeaer and is right.
radios use about 1/10 th the power of brake or blinker
blinks are 1amp, radio is 0.1amps or even less. so the radio will in fact run on a near dead, battery, even 10vdc *****.
the starter uses 3000 more power to crank and engine 300 amps
so the battery is dead. (or caused by bad alternator and you ignored the cluster charger lamp>?
here are all causes (not guess a test for each to prove it)
1; BATTERY DEAD.
2: ALTERNATOR DEAD CAUSES #1
3: JUMPER CABLE JUMP STARTS WORK (AAA TOW TRUCK DID IT?) or buy a battery charger and charge up the battery or barrow one good from 2nd good car. the battery swap trick.
4: NOT ABOVE. (ORDER MATERS) I then shift from PARK to Neutral and engine magically cranks, bad PNDRL switch.
5: bad starter relay. (if starter dead but relay is silent took, bingo relay or #4 caused)
6: stick shift gear box truck, clutch pedal switch bad, acting just like #4, and for the exact same reason bad switch.


if stranded, Not told
#4 is first. omg I'd driving home the users guide even tells starter cranks fast in NEUTRAL too, foot on brake.

taking the battery leads of a running alternator is one sure way of destroying the alternator
if you think a battery is dead you have it load tested and replaced if it doesn't meet the test
what you should be doing is taking the vehicle to an accredited auto electrician and having the battery load tested and the alternator and voltage regulator professionally tested for proper operation

Not on new vehicles , you never ever pull a battery cable while it is running ! A voltage spike can take out electronic components ! That was 60's an maybe a few 70's vehicles ! That change when they started using transistors in voltage regulators an in engine modules. If it is show 14 volts it's charging ! I will send a link on how you test the charging system. How To Check Charging System EricTheCarGuy

Have a load test done on the battery to check for cell failure as the alternator may be putting all the current into a shorting battery. Check the output of the alternator as the regulator may be faulty. Alternators produce 14.5 volts at 2000 rpm and the current is set according to requirement. That is with 14.5 volts and full current draw the alternator is capable of producing the rated amps ( up to 120 amps) If you have extra power requirements ( driving lights --massive amplifier) the total current draw may be more than the rated amp of the alternator and so the battery will eventually run down and there will be insufficient power to run the ECM and it will stop.

If charging light is on, it means some thing in the charging system is going bad. use a test light!-- battery voltage at battery when truck is off should be at least 12.6 or better, if alternator was charging good. if less than 12.4 and it is charging ok. battery is going bad. when engine is running, at the battery there should be at least 13.8 to 14.2 volts or better.if alternator is ok, all checks are done at the battery posts to determine voltage. Hope this helps you out! if less than 13.8 or lower while running. alt, is bad.

You may need a shop manual to get the wiring diagrams and test procedures.
The alternator output should be around 14 volts unless you have a heavy load such as headlights or the heater blower on high.
If voltage goes above 14 the regulator could be faulty even tho you say the alternator checked out ok on a bench test.
The regulator gets a power signal from the gauge on the dash to energize it. There could be a loose connection somewhere in the charging system, or something in the instrument cluster. Even the key switch could be a factor.

I had my ford 91 ranger checked and both were good, plus alternator was in the green? But kept killing batteries and would not start without a jump. I replaced solenoid, starter, and battery. Finally removed the alternator and the BRUSHES were making contact just enough to keep my truck running, but when lights or any other accessory was used the truck would quit. New alternator and starts every time and can run all accessories without problem. Check the brushes on the alternator.

Battery light indicates alternator failure. If you have a voltmeter, check voltage at battery with engine running. Should be at least 14 volts. If no voltmeter, remove alternator and take it to parts store for testing.
If the alternator is bad and that is your only problem, the truck should jump start, but it will not go far unless the battery is charged. OK?

could be the wrong battery check the craniking amps to see if u got the right battery sometimes these auto parts stores give the wrong item also make sure your cables are clean when clean pour some coca cola on them so they dont corode

Fusible link blown ? With a voltmeter check for B+ voltage at the heavy gage wire on the back of the alternator .Is the charge indicator light lit on the instrument cluster . Do you know what a wiring diagram is ? Free wiring diagram here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model and engine size. Under system click engine ,then under subsystem click charging . Click the search button then the blue link . Watch video on youtube checking alternator electrical .Power & ground !
Functions of an Alternator in vehicle
How to Test an Alternator