My 1999 ford ranger 3.0 automatic v6 has had issues with it not charging after I replaced my alternator I determined it was a bad battery after a series of tests so I replaced it now my truck is over charging and I can’t figure out why I’ve done most things I can think of and can’t fix it please help it’s a

 

Welcome to the forum

You haven't listed the test you did???
Or the voltages?

After a "good" battery has been sitting for 4+ hours it should have 12.3v to 12.8volts
New battery can be as high as 13.0v
12.2v and less is a drained or bad battery

Start engine
Battery should now show 13.5v to 14.8volts
If under 13.5v then alternator or is wiring are bad
If over 15v then voltage regulator in the alternator is bad, new or not

After engine has run for longer than 5min battery should now show 13.5v to 13.8volt, this means battery has recharged fully
(some newer battery types like 14.0v so thats OK)
Turn on headlights and heater fan to high
retest volts, should be the same as before
System is working fine

 

It was going up too 17.4 volts when my truck was running it was resting at 12.8v because it’s a brand new battery as of today so should use my warranty and get a new alternator all together or just replace the regulator

 

Whole new alternator


Alternator has 2 12v wires and one on/off wire from vehicles charging system
The smaller light green wire on the 3 wire voltage regulator connector, this is the ON/OFF switch for alternator, its also the Battery Light wire, when it has 12v alternator will turn on

The larger wire on the stud/nut terminal goes to Battery Positive via a Fuse or fusible link, so always 12v
The smaller Yellow wire also on the 3 wire connector is the Monitor wire for voltage regulator, its also connected to Battery Positive via a fuse or fusible link, so always 12v

When light green wire has 12v the voltage regulator turns on and sends the Rotor brushes 9.5volts
When rotor is spun by the engine that 9.5v should produce 14.5v
The voltage regulator varies that 9.5v lower or higher to match PUSH BACK from vehicles electrical system
The Yellow wire has the PUSH BACK

Any electrical system has pushback, say the system needs 30amps, once it gets to 30amps it will pushback, no more amps needed so a voltage regulator will settle in at that voltage, say 8.5v
If you turn on the headlights, then system need 35amps so pushback drops and voltage regulator increase voltage to say 8.7v, until it gets pushback again

When you first start an engine Battery is drained so low pushback and voltage regulator can do up to 10v, close to 15v out
But that will slowly drop as pushback goes up as Battery gets to full recharge, so 3 to 5min or so

17volts means voltage regulator is sending rotor full volts, 12 to 13volts so BROKEN, not regulating anything