Battery light stays on after changing battery,alternater & plugin.

Trouble shooting required:
What voltage is do you get with a multi meter at the battery terminals when the vehicle is running. (looking to see the alternator is putting out the required voltage)

What voltage when it is not running & during cranking. (testing the quality of the battery)

Does the battery go flat overnight? What if you disconnect the battery overnight? (Looking to see if something is draining the battery when the vehicle is not running)

That suggests that the problem is in the harness, something in the connector or wiring is causing an open circuit. You will need to have the circuit tested to find the fault. Ford alternators have known connector issues & new aftermarket connectors are readily available at most auto parts stores.

Troubleshoot first and then change parts! What was the original problem? It just won't crank over? The alternator just charges the battery the voltage regulator keeps from putting too much of a charge into the battery. Was the battery going dead? Did the vehicle start when jumping it with jumper cables? Too many unanswered questions to offer help, sorry.

Battery light usually means the alternator is not charging, get yourself a multimeter, select Volts, put red probe on positive and black probe on negative while the car is running, it should read above 13 Volts, not higher than high 14s, if it reads 12 volts or lower while engine is running than your charging system, alternator mainly, needs attention, any decent mechanic can check this in 2 minutes.

Just a thought.......... If the alternator is not grounded properly to the chasis , it will not charge , and the charge light probably will not come on either. Check for loose , or corroded ground wire or strap.

sounds like your alternator isnt functioning correctly.
you can have this tested at a local garage, normally for free. when the engine is running, it should show around 14 amps on a multimeter. also check the battery is serviced. check the fluid levels and a full charge

check your charging system. It may be the reason you changed batteries. The charging voltage should be in the following range 13.6 - 14.2 v. The lower the voltage the higher the rate of charge. Good Luck

I believe the rebuilt one is not good too. If the battery light stays on it means that the system is not charging. Did you connect all the wires the same way

u may have parasitic load what that is when like somethin on the car stays on even if u shut everything off causing to drain the battery

Mazda Mpv 2000 I also have the same problem, the alternater is testing good- 14.12Amp, so what is the problem the battery light will not go off.