I have a 72 chevelle that is having charging problems. I took the first altenator back because I thought it was bad!!!!!!! Using a amp meter and the old remove the negative battery cable trick!!! This is pretty much stock big block ss no chopped up wiring harnesses no slicies what so ever, so I am at a loss please help. Oh yea there is a new altenator on there that has the same issues!!!!Please help!!!:confused:

If the system is stock, you may still have the original voltage regulator. If so, try replacing it.
If the alternator has been replaced with a new "updated" alternator other solutions may apply. Could it be a 1-wire, Si or CS alternator?

The altenator has three wires. Also I do not know where the voltage regultor is. YOUR help would be appreciated!!!!!

Take a look inside the engine compartment, should be mounted to the radiator support behind the drivers side headlight. Probably have four wires in the connector, and a single wire condensor mounted to the side which has a lead to ground. Roughly 2" x 3". Easy to unbolt and replace with a new replacement. It sounds like an original alternator, and if so, 2 of the wires from the voltage regulator will go to the alternator and terminate in a 2 wire connector that plugs into the alternator. The 3rd wire is probably mounted to the positive stud on the lower rear of the alternator.
Here's a link to OPG which has a picture of the voltage regulator.
http://www.opgi.com/product.asp?topcatid=10&chapterid=645&topvalue=0&newflag=0&grpcode=14599&yearrange=1972

What is the voltage measured accross the battery:

With the engine and everything turned off?
With the engine idling?
With the engine reved up to say, about 2k?

Are the battery terminals and all grounds clean and tight?

Replaced voltage regulator yesterday still not charging!!!!! New OPTIMA red top battery, both new cables. Runs about 11.22 give or take idiling, reveving will jump up to about 11.99. Makes no sense to me. Still dies when removing the negative battery cable. It almost died this morning after dropping the kids off at school!!!!!! The kids love for thier friends to see them in the car and dad likes to get it sideways for the kids!!!!!! Motor is 454 .60over, 840 heads from 1967 corvette 427 625 lift 303 duration @50 all roller 850 AED carb {don't like it} 5-6 mpg. Dyno'd at 596hp all steel which is what I'm proud of ALL STEEL. Back to the problem running 6al mallory hei vaccum secondary normal radio no amps no spliced upwiring. My kids say please help they love to ride!!!!!!!!!!!! :o

Gotta be frustrating! Maybe have the parts store check out the alternator output again.
Battery voltage, not hooked up to anything, should be approx 12.6 volts plus. The alternator, hooked up to the battery in a running car, should be in the 14.6 volt range, higher with higher rpm. Check the hot lead to the alternator, and also the leads to the voltage regulator to make sure they are in good shape etc.
What I did was to check for unseen draws on the battery. I disconnected the negative cable of the battery, and hooked it to my multimeter, set up for 10amp reading, one lead to the ground cable, the other lead to the battery ground. I then pulled all the fuses and installed one at a time, with the ignition off, and checked each circuit for draw. This helped me find a bad circuit with a short to ground. Turned out to be the radio itself.

Pulling any wires off while the car is running is a good way to ruin the alt or vr.
Below is a good write up by Peter F. on checking voltage regulator/charging system.

The regulator brown #4 wire is connected through the light bulb to 12V whenever the key is in the ON position. The other end goes through a set of points in the regulator and then out the F terminal to the field winding in the alternator. So some current begins flowing in the field winding from this connection. The little bit of current flowing produces a weak magnet field in the alternator and also lights the bulb.

When you then start the car, the weak magnetic field from above begins rotating which makes the alternator producing a little bit of voltage. This voltage is fed from the alternator to the regulator on the white regulator #2 wire. This wire connects to a coil in the regulator and turns on a contact when the voltage goes above 3.2V.

Once the contact turns on in the regulator the #3 and #4 terminals are connected together. Terminal #3 is battery power so this puts battery power on both sides of the bulb and turns it off. This means the brown #4 wire should go to +12V. Also, this connects the field terminal right to battery power but still going through the points.

When the battery voltage goes above a set level, the F terminal is disconnected from the battery power by the points I kept mentioning. Then the voltage drops and the points close again. This on-off cycling happens rapidly and is how the voltage gets regulated.

From the above (KOEO = key on engine off and KOER = key on engine running).
F or #1 terminal (field) - KOEO = #4 slight voltage, KOER = 9-12V typically
#2 terminal (sense) - KOEO = 0V, KOER = >3.2V
#3 terminal (Battery) - KOEO = 12V, KOER = 12V
#4 terminal (light) - KOEO = F slight voltage, KOER = 12V

By 12V above I mean battery voltage, which may be 12V when engine is off but could be up to 14.5V when engine is running.

Check the light: Ground the brown #4 terminal wire at the regulator. When grounded the light should come on. If you don't have a light then skip this test. Test this with the connector off the regulator.

Checking the alternator: Jumper the blue wire F terminal to the battery post on the back. This should make it easily crank out 16+ volts. Next, connect a troublelight between the battery post and the F terminal. The light should come on and you should measure > 3.2V at the other alternator terminal. If it passes these tests, then it's in the regulator or wiring.

Checking the wiring: At the regulator connector jumper the brown light wire (#4) to the F terminal (#1) and you should be able to measure >3.2 volts on the other alternator terminal or terminal #2 of the regulator connector. If these tests pass, it is in your regulator.

When doing these tests, make sure you turn off or pull the fuses for any added electronics that you can. The alternator test can produce enough voltage to damage stuff.

Peter