Alternator not charging

Hi, my info showed this for S10 four cylinder alternator wiring diagrams with a guide to help you test it

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.

Engine running, take a reading at the alternator bat terminal. What is the reading?

Check the three things in pic that I have pointed out and yes still check the brown wire for a bad connection. But the fusible links should have same voltage both sides and not just one or two strands connecting them

Use an inexpensive digital voltmeter to measure the battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. If it's low, suspect the generator. It is real common to go through four to six of them on GM products, after the '86 models, in the live of the vehicle. To reduce the number of repeat failures, replace the battery at the same time as you replace the generator. As they age, they lose their ability to dampen and absorb the huge voltage spikes the generators produce due to their design. Those spikes can destroy the internal diodes and voltage regulator leading to the repeat failures, and they can cause running problems due to interference with computer sensor signals.

Here is a guide to help

https://www.2carpros.com/articles/how-to-check-a-car-alternator

The fuel gauge should find its way to the proper position when you fill the tank. It looks for the shortest way to the desired setting and that might currently be clockwise against the stop.

That was a test done many years ago by people who didn't understand how these simple systems work, and it was done on cars with no computers. Many cars today with perfectly good generators will stall when the battery cable is removed. Also, with one shorted or open diode inside the generator, the engine will still run but you will lose two thirds of the generator's rated capacity. You need a load test and a ripple test to find that. The battery is the key component in helping the voltage regulator control system voltage. Every year I did a demonstration for my students on what can happen with no battery in the system. It is REAL easy for system voltage to exceed 30 volts. That will destroy the internal diodes in the generator, any light bulbs that are turned on, and a number of computers. Use the voltmeter. You can find perfectly good ones at Harbor Freight Tools for $4.99.

Do a battery drain test

Battery drained in the AM only its not an alternator and most likely something is draining the battery over night

It sounds like the alternator has gone bad I would replace it with a rebuilt unit. Here is a guide that will give you an idea of how to do the job.

https://www.2carpros.com/articles/how-to-replace-an-alternator

Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers, Ken

Good luck
let me know

Also you can use a test light to connect the same way and watch the light to go dimmer as you pull the fuses and look for what is causing the drain
Start pulling fuses make sure that the door is closed and or the door switch is off

Bad ground will not cause a draw
Defective radio would if have an electrical door locks, stuck actuator would light on in the trunk would defective diode in the alternator would
The reason for the battery is draining something is staying on
Have to locate and find
Key off and all accessories off
If need to access the inside of the car make sure door switch off and not turning the inertial lights on Light should dim when to almost go out when no more draw and pulling fuses is to locate that circuit