2007 ford five hundred limited battery/check charging system

So the check "Advance Auto zone" does on the bench does not test for the control input and output? If not then how can the alternator work on the bench... mine just started doing this today. Alternator tested ok at AAP. Alternator was replaced several months ago and ok up till now. Cleaned grounds, and batt. terminals. Voltage is 12.4 ideling and batt dash light on but when running down the road it clears up and battery voltage jumps to 14.1V (Cigarette outlet LED meter) dash light goes out. But at a stop it drops out again... 3wire plug on alternator is seated but previous mechanic broke locking tab. Is there any suggestions on how to furter dianose issue?

If you unplug the 3 wire connector on the alternator it is supposed to go into limp home mode and charge at 13.8 volts , "self energizing with the however many r.p.m.s of the turning of the alternator via the belt spinning? I have been trying to fix the same kind of problem on a 2oo7 ford five hundred... I am guessing that is maybe how the main auto parts stores can bench test them? I.d.k. I'm Going to have the 3rd alternator tested tomorrow before installing it ...( I just came across this little bit of information ...this is according to the training seminar that remy put out, on a computer controlled 6th generation ford with its so called smart alternator) with no signal from the e.c.m. it goes limp af mode! also, there is a ton of things that it could be besides that ... It could be that some brainiac put an aftermarket stereo in the car, a blown fuse, bad computer, the one I am working on has not shown charging at all with this unplugged, so.. tomorrow, I will know for sure and I will post the results... I have well Over fifteen years in a professional auto repair shop, many more years beside that.... Just frustrating on this gem ... I did the alternator 1 time and the wiring was worn through at the extra length of wire from above the alternator there is a second plug in the harness replaced without the extra plug to eliminate one more future problem basically from the new 3 wire plug to the fire wall , btw this all stemmed from all the motor mounts being bad in the 1st place... She had an alternator put in and 2 batteries before I saw the car. I repaired the wiring first and battery cable , main wire to alternator fuse links , ( a little bigger for good measure) after checking it and seeing exposed copper and it was mostly the o2 wires but I did all three of the alt.wires, and the wiring to both o2 sensors, and the main power wire that goes across the back of the engine , checked the battery fused power ...runs across the front end by the radiator then across the front of the engine down to the one side of the plug on the alt. The 2 wires split right before that turn in the harness . They go to the fire wall to the e.c.m. ( when you have a good scan tool that will let you view you it, you can bridge the two together to watch it command and receive the secret hand shake ); smart as hell right . Just another piece of garbage ford innovation ... On how to get your money with hours of diagnostic time and get to save the day with their service dept.s As they mother chuck all the indy garages with their sub-standard inferior parts from "not ford" suppliers ... Of course if the mass holes would just release these little tidbits of simple info like wiring schematics and a little theory and operation back on Autozones website, it used to be so nice, with the little bit of Alldata, but I'm sure they were losing a ton of money letting the public have information for free... ... Maybe a slip in the box when you buy a brand new alternator at the part store or maybe if the information would show whether or not the computer was trying to command the alternator when you buy the best scan tool they had for 400 dallas or if it told you like it has a soft start and won't charge right away when you first start the car or when you have it all like registered with its fake little repair helper you download on your smart phone or if a Google search , with this kind of stupid alternator problem it could show the simple way to test it and the wiring. I myself also thought I was going to have to drop the subframe to change it.... You don't . It is easy to do, turn the steering wheel all the way right after the outer tie rod end is taken off the knuckle... Just the taper part ... One more nut, that is kind of like the one that ford has done to people here in the but, wait I don't want to get off on a rant here about ford garbage or the main auto makers that don't have a recall on some of these things ... Anyway, yah. The alternator has a little plastic venting thing that is held by two of the bolts of the alt. Then the one to hold the alternator up without blah blah just take the cover off then the wiring or something spin it like a tiny bit and it slides right out so easy a cave man would complain about the incorrect book time that the dealer criminally gets away with charging ... Then they find all your other problems and give you a hopeless outlook on your rebadged ford taurus and tell you they stopped making the 5oos and started back with the taurus... It should be stopped ... Any kind of car company that does these things to our own people without answering to it is evil in my book. Go ford....could you remember to put a little lube on that and come help me hold this while you get a nut... Ahh thanks... It should not take this much of my life away...just for a bad alternator ....in an American car... Just saying... But hey, who am I to have an opinion on anything ? I voted for trump...