or is it 'worse'?
lets start with what i got: 2001 ranger, v6 4L EFI, auto trans, 4x4. stock motor, no mods.
heres the problem: 'battery' light came on when i got home one rainy night and parked. it was idling at normal rpm. (800-900) when i brought it up to 1300-1500rpm the light would go out. i figured it was due to a wet belt and just went to bed (no noise from the belt, ever.) the next day it was not raining, the light came on as soon as the motor warmed up and the rpm went to normal. and the light went off as soon as i started driving. as the day went on the light would start to flicker around 1300-1500rpm. and by the end of the day (of off-on driving) the light wouldn't shut off unless the motor was around 2000rpm (driving or in neutral). At high rpms (4000-4800) the light will flicker a few seconds before the next gear, but never stay on for more than a flash.
the battery is at 12.3v with motor off, 11.5v with it running and headlights on.
shut off the headlights while motor is still running and its about 12v even.
battery connections are both good.
all connections to the alternator are good too.

this is my first post, i know i forgot some piece of info but i cant remember.
all help is appreciated, including help on improving my posts.

When mine lit up I googled it, and it said alternator failure. Replaced the alternator, and all went well.

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Thank you for the input. My concern is that my light is not always on, so I don't think the alternator is completely dead. I could be wrong though. Maybe the brushes are almost completely worn?

take it to auto zone and they can test it...

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Sounds like the alt though that's what mine did and I replaced it and it was good to go.

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i was just trying to fix it now since i need my truck for work today but i called out of work and spent the day installing the new alt. ($170 w/ core charge) but the tensioner snapped when i tryed 'loosening' it so now i gotta get a whole new tensioner assembly

Go to a auto parts store and buy a volt/amp load meter ($20.00) before you buy anything. With engine off, Clamp meter on battery,( - black to black and red to red + ) should read 12 volts. With engine off, throw the load switch on meter and hold until wire elements in meter glow, should hold stedy at 400 - 800 amps. If either reading is not up to par, take off battery caps ( some times under a sticker on top of battery ) check to see if acid solution is up to the bottom of filler ports on baterry. Don,t worry if battery says maintance free. there is no such thing. if low, fill with ordinary tap water ( not recommened by manufacture but it will do) and put caps on. Charge battery with the lowest possiable charge on battery charger for a least three hours. Do not smoke or introduce any kind of flame when chargeing battery. When you pass electicity thru water it seperates the atoms (H2O) in the water and vents out of the battery. Hydrogen and Oxygen, same stuff they put the space shuttle into orbit ( very explosive ).

After chargeing battery with engine off, recheck voltage reading should read 12 volts or higher, no less. next flip the the load switch and hold till elements glow( about 10 seconds ), should hold between 400 and 800 amps. Its OK if it starts out high and drops as long as it does not fall below 400 amps. The higher the amps hold the stronger and higher Quality battery. If voltage or amp reading is not within these specifications, replace battery.

After checking and replacing battery if needed, start engine and check voltage. Voltage should read 14 -15 volts respectively. Any lower or higher alternater is not funtioning properly. If it is lower than 14 - 15 volts then you are useing the electricity in the battery to power the engine and related componets. If it is any higher then 14 - 15 volts then the internal voltage regulator is burnt out and alternater should be replaced.

If it is lower before replacing remove alternater from vehicale and bring it to a auto parts store. Most stores will check the alternator for free or a small fee, to see if it is working properly. If it is not working properly then replace it. Warning, Always disconnect negetive terminal ( Black ) from battery first, before removing alternater. If you don,t you can ether cause a fire,explosion of the battery or at the very least damage the electrical system permeantly!

If it is working properly then you have a wireing problem. Reinstall the alternater and using a multi meter, check that you are getting 12 volts on the field wire ( Large single Red wire )from the fuse box on the driver side fender under the hood to the battery and from fuse box to the back of the alternator. Put The pos terminal of a multi meter ( 30 volt scale DC ) on the field wire (large single red wire) on the back of the alternater. Put the negetive lead on bare metal of the frame of car. If voltage is not 12 volts than you have a fault in the field wire between then fuse box and the alternator. Remove the fuse for the field wire and useing the multi meter to check if you have 12 volts on one side of fuse holder. If you don't, use the multi meter ( set on continuity ) and check the fuse. if good check the field wire from the out bound side of fuse holder to the alternator for continuity. If good then useing the multi meter set to DC 30 volt scale check the field wire from the in bound side of the fuse box. If you don't have 12 volts, check the field wire at fuse box, for continuity, from in bound side of field wire back to where the field wire is spliced to the red Pos cable of the battery. If good, un-tape splice at battery on positive cable. you will see a smaller wire at the end of field wire where it meets the positive cable. This is a fuseable link wich protects the field wire from over load. Check for continuity on fusable link. You must seperate the field wire from the fuseable link first.

If the fuseable link is good reconnect. Before i tell you what to check next i need to give you a 101 class on how electricity is generated in a generater or alternator. Please be patient with me. To generate electricity you ethier have to rotate a copper coil around a magnetic field ( ie Magnets ) or rotate a magnetic field around a copper coil. Alternaters do not have magnets in them so you have to create a magnetic field for the copper coil to rotate around to generate electricity.
When you pass a electric current through a coil of copper wire, a magenetic field is created around the coil. In a alternater a small coil Called the primary coil or winding is energized when you turn the key on creating a magnetic field. A second much larger coil called the secondary coil or winding rotates around the smaller primary coil induceing a large current (60,100 amps ect. ) into the larger secondary coil, which is connected to your field wire which in turn charges your battery and replaces any power be used by the engine and accessaries.

So we now must check to see if you have 12 volts going to the smaller primary coil. On the back of your alternater ( I have a 97 ranger and the positive wire of the primary coil is yellow with a green stripe), there is a two smaller wires next the field wire. Turn the key on and check the primary coil wire for 12 volts. If you do not have 12 volts, use the same procedures to check for any faults in the primary wire leading from the alternator back to the fuse box under the hood.

And that is that! I hope I did not confuse anybody. I also hope that this information will help you solve your problem. Good LucK.

ummm, ok save yourself a few hours and don't worry about that lengthy cut and paste procedure that pretty much has nothing to do with any of this.

Your alternator is toast. The light comes on when the key is on but the alternator is not generating power. What you described is text book failing alternator. It works at some RPM and not others. Perfectly normal. Unbolt the old one, bolt on the new one. After you finish fixing the other parts you broke

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hahaha thank you fireranger, i did end up replacing the alt. and got a new belt while i was at it. everythings runnin strong, and the battery is back up around 13v.

Sweet deal. Glad you got it fixed.

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