I have a 2003 ranger 4L. Battery died overnight, set charger overnight the following day, died that day multiple times after being boosted. Checked alternator, found out it wasn't for working. Replaced with brand new 95 amp alternator. Truck still wouldn't run, replaced with brand new battery. Runs and starts but still has battery light on. I charged the new battery up overnight and still the light is on.
Sometimes whenever I start the truck the battery gage will run up to high, to low then to right below half. While this is happening lights are going on and off(ie abs, battery light). No matter what the battery will not charge up to what it should be at. Any insight?

 

You need a volt/ohm meter, it will save you hundreds of dollars.

First never use a battery charger on a battery that is hooked up to the vehicle, remove battery cables then charge battery.
The newer electronics can be FUBARed by battery chargers, and even jump starting.

Second, measure battery voltage with key off, set Meter to 20vDC(20 volts DC or just DC volts)
New battery will be 12.8volts
5 year old battery 12.3volts

Now lets test alternator wiring, key still off

Black meter's wire on battery Negative, Or engine metal(ground)
Red meter wire touched to Alternator's B+(big terminal on back side of alternator)
You should have Battery Voltage, whatever you had above should be here.
If not, you have some blown fusible links

If you have Battery Voltage at B+ then unplug the 3 wire connector on alternator

There is a Yellow/white stripe wire, test it the same as above you should have battery voltage.
If not then a fusible link is blown

Now turn on the key
Test light green/red stripe wire, it should have Battery voltage but only with key on, this is the Battery Light wire.


A Fusible link is a short wire that is a smaller gauge than the main wire, it is used as a fuse, it will melt and separate without burning if too many amps are run thru it.
The reason they use fusible links is that they can tolerate a spike in amps without blowing out like a fuse would, and alternators can have amp spikes at first startup.

The splices for the fusible links can also fail, so if you find one of the tests above shows low or no voltage then you will need to open the wiring harness to follow the wire with no or low volts until you find the Fusible link and then check why it isn't passing voltage.

Disconnect battery's Negative cable when tracing the wire.


Read this thread, same year and model as your, and no charging just like yours: https://www.ranger-forums.com/genera...rminal-146422/

 

So I've tested the battery nothing on, 12.59v. Tested the alternator back(forget name) no voltage reading. Now do I trace back through the three wire harness/connector on the alternator?

 

Back terminal on alternator is called the B+, wires there should be larger gauge than most, if there was no voltage there then BOTH fusible links are blown or disconnected somehow.

Yellow/white stripe wire is connected thru 1 of those fusible links as well as its own so it will also have 0 volts.

The fusible links will be nearer the battery than the alternator, actually nearer the Battery Junction box than battery or alternator from this(\/ \/) drawing.

So I would start at that end and follow the Larger Red wire from junction box into the harness, you should find a splice, S130, with the 2 fusible links connected to the larger Red wire.
As per the drawing these 2 fusible link wires will be gray, and both will connect to a Brown fusible link at their other end, splice S131, Black/orange stripe wire will also be on that splice, S131, it runs to B+ on alternator.

Most auto parts stores sell fusible link wire, the color is a manufacturers choice so not important, the GAUGE is important, so 12 gauge fusible link for B+, or 18 gauge fusible link for Yellow/white stripe wire.

Remember.............UNHOOK THE BATTERY when tracing wire, these wires got lots of AMPs

 

Did the tests as you stated, checked the fusible links. No burns or flaws in the connections. Got a second opinion and found a loose wire touching the frame, shorting out the system. Thanks again for the help.

 

Thanks for the update, good work finding the short