Voltmeter reading? Accuracy? Options

[SKL1]

Trying to figure out how accurate the OEM voltmeter is in my '73 2.0. To make a long story shorter the engine in the car is a much modified 1.9 from my '71, with approx 120K miles on the alternator.

Voltmeter reads around 11V and drops to 10 if I turn on the headlights. Immediately goes back to 11 or just over that with the lights turned off.

Replaced the voltage regulator this AM and did a test drive with no change. Gauge never gets close or above 12V. Makes me afraid to drive it at night with the lights on and go very far.

Do I need to go through the hassle of rebuilding the alternator or trying the alternator from the original 2.0 engine that has about 70K miles on it?

Better way to get a more accurate reading of actual voltage?? I hate electrical issues!!!!

TIA.

[emerygt350]

It means either the alternator is shot or your voltage regulator is shot. The vr is 35 dollars so start there. If that doesn't fix it then the alternator. Not terrible to replace or pay for. That difference between the battery and the gauge is what you get unless you alter the voltmeter wiring.