After changing alternator and voltage regulator. Still not charging. 2nd $15.00 regulator replacment

The voltage regulator is built into the alternator.
https://www.oreillyauto.com/shop/b/charging---starting-4716/voltage-regulator-735/bcb09f5b993f/1999/chevrolet/astro

The way to check for an over or under charge is to connect your volt meter to the battery, before starting the vehicle.
You should have a reading of 12.5 to 13 volts. If it's 11.8 like you stated or less, it means battery is not fully charged, or it's bad. Now start the car & check voltage again while running the engine, the voltage should exceed 14+ volts, this means your Alternator is charging, the voltage should drop after battery has been charging for awhile. When you turn the engine off after letting it charge the battery, & if the battery is good, you should now have 12.5 volts to 13 volts.
Now to answer your question, the Voltage Regulator is inside of the Altenator, I believe you xcan take the alternator apart to replace it, or simpler to just replace the complete alternator.

If the battery is no good,then you will hear the alternator
hum all the time, trying to charge it

Check for diode problems & A/C Ripple on the circuit

Check all vehicle grounds (wires)

If the wiring is good & the light comes on, it isn't charging
properly,have you not metered that,voltage,amperage &
ripple

You can go through 3 alternators from the auto part chains, to
find a good one.

Have you replaced the voltage regulator?
Unless you have changed the charging system and eliminated it, the alternator does not have a built-in voltage regulator like the newer ones do.
Be blessed.

Due to the nature of the battery technology used with vehicles the alternator is mostly incapable of charging the battery. The car alternator is designed to keep a fully charged battery fully charged and to provide all the power for the car equipment.

The alternator charge rate is regulated by a voltage regulator. Because the alternator output is connected to the battery, the alternator and battery voltage will be the same and the voltage regulator monitors that voltage.

The lower the battery voltage the more output the alternator will produce in order to correct the situation but because a lead acid battery has a high internal resistance to accepting a charge the terminal voltage will quickly rise to the alternator regulated voltage and fool the alternator into thinking the battery is fully charged when the output will drop to the order of just a couple of amps.

Switch on the headlights or a similar load that will lower the battery voltage and the alternator will increase it's output again - but only by the amount of current the headlamps or other load is consuming.
It matters not what the alternator rated maximum output is, it is designed to provide only the necessary current and no more.

The only time an alternator should ever need to produce maximum output is when on a dedicated testbed and then only for a short duration to avoid damaging the unit. Testing the current output on a modern vehicle is not recommended except for the regulated voltage testing and a rule-of-thumb output test where all equipment is switched on and the engine speed raised while the battery voltage is monitored.

Most modern alternators use an internal voltage regulator but a few systems use a separate voltage regulator. No alternator rebuild would be complete without a regulator test and probably a new or replacement regulator, which is where the majority of charging system problems are, or the brush gear.
Assuming the wiring is ok, no alternator should suffer any harm if the voltage regulator and auxilliary diodes (if fitted) are in good order though fitting a defective or a discharged battery can cause it to overheat and be damaged.

The alternator usually just about stops producing an output when the battery voltage is in the region of 14.5/14.8 volts.
Your description indicates the voltage regulator is not working correctly - unless 40 amps was being consumed by the car equipment the alternator should not have been producing 40 amps.. I suggest you also have your battery tested

Hi,
If you were originally having a wild fluctuation in measurement at the battery the voltage regulator would have been shot. I'm not sure of what the condition was of the original alternator. But I would definitely have changed the voltage regulator. A bad regulator can ruin a battery and all sorts of other things. If you are now getting wild variations in voltage
1st Purchase and install a new voltage regulator. (probably about $20.00 these days.
Then check your new battery by doing the following:
1 Disconnect it from the truck's electrical system.
2 Charge it up using another vehicle and jumpers.
3 After disconnecting the battery from the jumpers, let it sit for a few minutes.
4 Check the voltage. If it is below 12 volts, the battery is shot. Replace it under warranty.
5 When you get the new battery, Install it in the truck and start it up. Then measure the voltages coming into the battery from the alternator and the new voltage regulator.
If all is well, your done.
If not. Pull the alternator and replace that.
Hope this helps,
Good Luck,
Mark

Regulator The voltage regulators that are used with the alternators on these vehicles are transistorized and cannot be serviced. If the voltage regulator is not operating properly, it must be replaced.

it is probably the regulator which is bolted on to the alternator

Here is what you need.



Please rate this a fixya

How long did the 2nd alt. last before it died? The voltage regulator is, I believe, attached to the alternator. Have u had the voltage regulator checked?