I would do a quick test.
test battery voltage, should be 12.3-12.8volts, new battery 12.8v, 5 year old battery 12.3v
Now if possible have volt meter hooked up to battery where you can see it and start the engine, volts should stay above 9.8volts.
If voltage drops more then could be a bad cable or starter motor going out, drawing too many amps.
After engine is started you should see 14+ volts at battery, but under 15volts
This is the "recharge voltage" the voltage regulator uses just after battery drain from starting.
This voltage should drop to 13.6volts after a few minutes.
Generally the voltage regulator will run a "maintenance charge" of about 1.1v above battery voltage, this will keep battery charged but not "cook it", above 14v long term will shorten battery life.
Once voltage is at 13.6v turn on head lights, voltage should drop and then come back up to 13.6v
Turn heater fan to high, same drop then back up.
Turn on everything you can thing of, lol, doors open, cargo light on, voltage should stay at 13.6v.
This drop and return is the voltage regulator working like it should.
If things don't come out as above then test the voltage at alternator.
Voltage meter black probe on battery negative, or good ground
Red probe on B+ terminal, large terminal on back of alternator, should read battery voltage here, i.e. 12.5v
Pull off 3 wire connector on alternator
Yellow wire with white stripe, red probe, should be battery voltage, if not Fusible link is bad
turn key on
Light Green red stripe wire to red probe should now have battery voltage, turn key off, voltage should be 0 now, this is the ON/OFF switch for alternator(battery light on dash), just FYI, if this is left ON then battery will drain.
The main reason there is a "accessories" selection on the key switch is so the alternator is not ON, and draining the battery.
New rangers have a "battery saver" relay, once the key is off and all the doors closed, the battery saver relay will start a 20-40min count down, once timer gets to 0 the battery saver relay will cut power to minimum, so if a dome light or glove box light was left on by mistake it should good off, it also cuts power to GEM module.
battery saver relay makes it hard to test for voltage drains, because you need to wait 20-40min. before you can see what the true amp draw is.
Last edited by RonD; 08-10-2015 at 12:03 PM.