so I am having a problem with my 72. I was driving my car to work every day(hr drive) and when I left work the battery would be very weak to the point it wouldn't start. so I replaced the battery alternator and spark plugs. I just pulled into work this morning and my volt meter was reading around 11v with the car running. I also noticed it was kind of sputtering upon hard acceleration also. any ideas? loose alt belt?

Check your grounds,
and
Is your light on in the dash?

Voltage regulator maybe and the generator warning lamp must be good and not an LED btw.

no light on the dash

just checked with a multimeter on my lunch while at idle its reading 12.3v. also stupid question (not very handy with electronics) is the voltage regulator in the relay box in the engine compartment? maybe where the alternator plugs in?

The VR is the 2"x3" box that plugs in to the middle-right of the relay board.

The voltage gauge in the center console is not an accurate monitor of the health of your charging system. It reacts wildly to headlights, brake lights, turn signals, etc. If you learn where it "likes to read" under normal circumstances you can then use that to tell when a light is burned out, but using it to tell when your car is not charging is not advisable.

If you measured 12.3V across the battery posts with your multimeter, then the system isn't charging at idle. Not fatal, but not ideal. If you measured somewhere else in the car, you could be seeing voltage drop to wherever it is you measured.

Otherwise, check the belt tightness, check the grounding path for the alternator, check the battery connections, and so on.

--DD

Does the Generator light come on when you first turn the key? If not the bulb is burned out and the alternator won't charge the battery. If you put the battery on a charger it will then start the car, as you drive it will be running on the battery not the alternator and it will gradually discharge the battery until it's too low to start the car.

1- gen bulb is hopefully not just been traded out for a LED - if so put the reg bulb back in

2- the sputtering is a result of low voltage on the system.

So if a new alternator was just installed it's not charging the battery -check connections and voltage regulator. If not what did the alternator harness look like? pretty good shape no "burns".

Or if the alternator is new hopefully its not grounding out to the back of the cooling plate (I think you would have noticed this, but a possibility)

Let us know what you find.

My money is on the harness

gen light does come on when I turn the key, no LED. is a 72 VR interchangeable with a 75? if so I should have a spare.

Try and see if the battery is charging with the voltage regulator. The battery terminals should read between 13-14 volts. you can jump two of the terminals on the relay board where the voltage regulator sits. You can see if the battery is getting charged. It is "D+" and "Df". Look up diagram of relay board 914. It should read between 13 to 14 volts at the battery terminal.

Buck

Sounds like it's time for a new Bosch battery baker (VR). When they go bad they can sometimes apply too high of a voltage & cook your battery. FYI.

You can get a good idea of how well your charging system is functioning by doing a few easy tests with a voltmeter with the engine warmed up and idling.

The VR tests are done at the relay board by jamming the voltmeter probe into the 3-conductor connector to the VR.

Battery:
Test battery terminal POS (battery post, not the clamp) to chassis ground, not engine. Should be 13-14V
Test battery terminal NEG (battery post, not the clamp) to chassis ground, not engine. Should be 0.0V

VR:
D+ to chassis ground, not engine. Should be 13-14V
DF to chassis ground, not engine. Should be 6-10V
D- to chassis ground, not engine. Should be 0V

The VR D+ measurement should match the battery POS measurement.
The VR D- measurement is checking the grounding of the alternator to the fan shroud>>engine>>transmission>>transmission strap to chassis.
The VR DF measurement is the exciting voltage to the alternator armature. The higher the voltage the higher the alternator output is.
The battery NEG measurement is checking the battery cable to chassis.