Troubleshooting car starting problems for a 93 Cadillac Deville

Deville 92 old. lots to find bad that old. !
here it is, ID #2 below
you were told wrong, the reg is inside the ALT, actual.
the internet lied again.; 1/2 the time, asking 8year kid same.

the top parts sellers online,shows, no REG outside, so strike 2 on reg outside.

learn to keep that old (how old is it?) battery charged fully until car runs perfectly. or it can take 1/2 to jump start it or worse. dead batteries do not start engines and overload the poor donor cars electrics, doing so.(jumped)

once battery is new, or charged or load tested in a real shop
start the engine, see if GEN/CHARGE lamp goes out.? on dash.
if not alt is bad. wow no fuse then, scary then. lots of car fires.
or use voltmeter idling, at bat terms. 13,to 15vdc good below ALt is dead
140amp alt here.

https://www.rockauto.com/en/catalog/cadillac,1992,deville,4.9l+v8,1025738,electrical,alternator+/+generator,2412

If it wont crank over the battery might be to weak to start the car but just have enoughf juice to run the electronics in the car.
Or the starter died.
1st charge the battery up and see if that works.
2nd if the fully charged battery dosent solve the problem then replace the starter.

It could be a bad alternator not keeping the battery charged. You need to check the starting and charging systems with diagnostic meters to find the problem.

Unhook battery, let sit for 5 mins and hook back up.

2 possible problems could be low charge on the battery (if it's the original battery it's definitely time for a new 1) a slick serpentine belt could also cause a low charge on the battery. A bad starter will require more and more energy to start the car until eventually it won't start the car at all.

It could be the starter. It could be a bad battery cable connection. Have you tried jump starting the engine. If it starts, then most likely it's to do with the battery or charging system.

the alternator controls the light directly through wiring. So, it's probably a bad alternator.

Before you start changing everything Test. Check voltage at battery with key off it should read 11.7 to 11.9. Now start car voltage should be 13.5 roughly, rev engine to 2000rpm and voltage should climb another 1.5 average. Let off rpms and it should drop back to intial reading of around 13.5. If things don,t test right then its cables or altenator or ground from battery to altenator housing.

When it won't start check for spark , pull a spark plug wire an hold it near ground (metal on the engine ) have s helper crank the engine . Is there spark ? If no check power an ground at the ignition control module , check control . In side the ignition module are transistors ,these energize the coil (control spark ) It can be tested with a test light . Check out scanner danner videos on youtube . But if there is spark , spray some starting fluid into the engine throttle plate an see if it starts then . If it does you have a fuel problem .

Recheck the charge on the battery,make sure it's fully charged.Check all connections at the battery and at the starter.Possibly a bad starter.If the starter is ruled out,then look at the teeth on the flexplate/flywheel.I would remove the starter and test it.