Alt. not charging replaced alt no charge battery dose it have a fuse of some kind this is on 2008 mercury mountioneer 4.0

NO ENGINE TOLD OF 4 SOLD NEW DAY1.
NO, AT IDLE IT CHARGES TOO !
800 RPM NORMAL NOT 400.
THE OLD ALT HAD AN EXTERNAL REGULATOR ,AND IS BAD THIS OLD, 55AMP ALT
ALL FUSE GOOD FOR SURE RELATED TO ALT
FUSEBLE LINK TO ALT HUGE LUG NOT BLOWN

THIS CAR HAD 2 DIFFERENT KINDS OF REGUATOR
USE THE CORRECT ONE,
MAY CAR THIS OLD ARE UPGRADED TO ALT WITH ITS OWN INTERNAL ELECTRONIC REGULATOR..
I HAD 1970 CAR AND THEY SELL ELECTRONIC EXTERNAL REGULATORS. AS AND UPGRADE, WOW WAY BETTER.

there are only 3 parts. but the causes are 25 or more.
1: belt missing slipping,
2: engine rpm below 800 RPM (lots of ways ,ask )
3: ALT had.
4: wiring to ALT bad.
5: bad battery or its connections, (wires)
6: bad fuse. see fuse link a11? on fFM page 20?
7: car is PCM alt controlled, it can be bad too. see 2 field wires on ALT and PCM on page 20? below?
8: battery temp sensor bad. making PCM think battery overheats.
the fSM covers all tests above.

pick car here, then pick charging.
5 alternators used on the 5 diffr.engines. got the wrong one?

the see wiring diagrams at end and chapter 20 inside, charge.
pdf page 118 for gas engine, if diesel next few.

The Charge lamp comes on with the Alternator fails to keep battery charge going. (lots of way to fail, and ALT Is 100% good) it's a system. each part of it must be good, end to end.
so...
i put my voltmeter across battery, i start car, i see 13.3 to 15vdc, alt is good.
no? , i see now, 12.2v. ALt is dead, (i didnt say bad) and battery is sightly discharged, 12.6v is charged. (key off, rested voltage)
This 12v tells me the ALT is shut down. only why is the question.

how can any charge system fail,
bad battery tops the list here, they LOVE to fail.
1: belt slips.
2: belt missing
3: bad alt.
4: bad wires to ALT . (corrosion on any wire or lug)
5: fuses blown , any listed below.:
your alt is not an ECU controlled, alt ,its 100% self contained

did you ever remove the ALT and blow the 100 amp fuseable link
the first step of any alt pul, is the pull the NEG, battery lug or BOOM.

im logged in to alldata.com so can you.

and what do i see.
a 5 wire ALT. one is the frame ground, so it must not be rusty or..... it fails. frame to engine block. no rust here.

wire L , yellow.goes to dash LEDs (alt failure idiot lamps) (this works)
wire. S white goes to ALT 5a fuse, is it blown?
wire :B B/G color, goes to the 100 amp link fuse. (blown>?)
wire IG Red-white, goes to a fuse marked 10A gauge.

i think the IG wire is the voltage sense wire.
no sense, no charge. I think the whole I/P dash cluster goes dead when this fuse blows.

The S wire is the boot strap voltage sense, it wakes up the regulator .
if open , the reg stays asleep, as does ALT.
Alternators can not self start, the regulator has boot strap device
that cures that. called self excitation. so this wire is critical.
All wires except the L wire is critical. in this case.

the B wire is the big wire, it charges the battery . 50amps or more..

any of the 5 paths open , kills the ALT dead.
The REG inside the ALT can also shut it down.
eg: battery bad, with huge cell resistances. total.
eg: overvoltge for any reasons. including attempts top run car with no battery, (dont ask)
eg: over current (battery cells 1 to 6 shorted) or 25 KC lamps added.
eg: over temperature shut down.

that is about it.

Check for a blown fuse, if I remember right Oldsmobile had a charging fuse in those years.

Is your battery any good? A bad battery will not charge or charge properly and be at the root cause of your issue.

Check your alt.. alt voltage output should be at least 13.2, sounds like it's not charging and your possibly running off the battery, as for the dash and tail lights, there both on the same system, check the fuse.

the altornator may have stoped charging,,but you will need to recharge the car battery first as its now very flat?

1) check 10A fuse in the batt. juction box (eng. comp.) hot at all times.
2) check the large red battery wire to the alt. for good conn.
3) make sure the alt. is grounded properly
4) gray wire sent from the alt. to the PCM
5) blue wire sent from the PCM to the regulator (alt.)
6) small red wire power frorm the 10A fuse
if all checks out and still not charge replace the alt.

I recently went through a battery/charging episode. Not to sound like the wise-guy, But! try a good battery and see what kind of reading(s) you can get.
Let me know if this is of help to you.

Check the small wires that clip into the side of the alternator, they set the Field coil in the alternator and could be causing the issue. Also, how old is the battery? If it's bad the alternator will cook the voltage regulator because it will be at max out put all the time.