Not charing check battery / good check alt. / good check fuses / not blowed car still not charging

How old is the battery? In general, vehicle batteries are considered 'old' after 5 years especially on bigger engines.
Using a volt meter or a multimeter set to Volts try this. With the engine off and the Keys out test the voltage directly on the battery. You should get a reading somewhere around 12.6 to 13.2 volts. Start the engine and retest the battery voltage. If the alternator is working correctly the reading should rise to somewhere around 13.6 to 14.2 volts.

cranks but wont start.
only a shorted starter can do that.
or alternator gone nuts but that blows the 60amp fuse seen here
you can do lots.
first and always first. check all fuse, (TEST THEM)
I had a car back in 1972 that (mech, really alternator reg)
that went nuts and blew up every lamp in car, at midnight far from home, in a bad neighborhood too.. scary, but engine ran.
your car is EFI,
and is only safe up to 15VDC< over that you blow up ECU
or if lucky (only the 3 ECU fuses blow)
is the CEL lamp working in the cluster,? if no the fuses blew.
the 3 fuses are
IG coil
FI
and dome.
there are 50 reasons for no start but based off one fact
i say fuses.
testing fuses. matters
if they look bad the are,
if they look good, they can be in fact bad,(called hairline cracks)
we test them did you? really test them,i do it live using a voltmeter
the meter NEVER EVER lies.
see? using a meter avoids going down the wrong path to H3LL.
(dog chasing tail)
now what if you measured the 3 power pins on the ECU behind
left speaker (sold my 91,4wd/2door, restored by me)
the ECU has power, (i have the schematic)
if it has power, the CEL must glow, or the ECU was burned up.
1991 are all 8valve cars, then
simple schm.
http://www.fixkick.com/ECU/8v-tbi-schematic91to95.jpg
full set.
http://www.fixkick.com/look/91-complete.pdf

starter. /charge.
http://www.fixkick.com/Charging/charge89.jpg

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 10 amp ECM fuse. Your alternator voltage is regulated by the ECM. If the fuse is good, consider replacing the ECM.

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.

you may connecting it wrongly , please check +ve and-ve both pole are to be fix with proper wire, if will do wrong it will blow fuse.

Hello there:
I would first refer to the owners manual to make sure that the fuse that is blowing is of the right amps also check the fuses under the hood too. than i would check to see if there is any shorts anywhere and get them fixed. You can also take the car to autozone and have the free diagnostics done on the vehical ok?
hope that htis has helped out some.
best regards mike

Rest at ease the 14 volts will not hurt your system idealy your alt will charge at around 14 to 14,5 volts at the alternator and probably have a slightly lower charge rate at your battery at around 14 to 13.5 at the battery this is completely normal