Alternator issue- maybe..., Voltage gauge and Charging light issues Options

[creeves84]

So I'm lost on this one- here is what I have. its a 1975 914 2.0, my issue is the following:

Car was running fine- went to put it in the garage and notice that the fuel gauge was on reserve (but had about 10 gallons in the tank), gave it a bit of throttle to move the car and the charging light came on. I looked at the volt gauge and it was not registering at all.

Thought it may have been a voltage regulator, as at times when applying the brakes- the gauge dropped from 14 to about 12 volts, off the brake back to 14 volts. Car was acting weird earlier, I think it was running off the battery only- tach was acting weird, seemed like limited power.

I replaced the voltage regulator- the gauge still doesn't read, charged the battery (new AGM). It was low at 11 volts with no load (not completely charged yet), started the car, tested the battery again with a hand held meter - no increase in voltage at the battery.

I'm thinking its the alternator but the question I have, is the volt gauge pulling the reading from the alternator and that is why its not reading? is the fuel gauge not working due to low power from the battery working off reserve? Am I going down the right path thinking its the alternator?