Alternator stuff

[Baz]

I have measured 12V across the battery terminal with car running at idle, likewise I have measured 12v alternator termina to earth.....
I am aware this should read 13-14 v.

Should I fix this or is 12 v input to battery gonna last. I seldom have any other accessory running aside from turn signals brake lights, and some times a digital radio.

Thanks
Baz

[spider2081]

I think the idle speed is important. Alternators shaft speed usually needs to be over 1000 rpm for the alternator to have an output abov the batteries voltage. What is the voltage when the engine is turning close to 2000 rpm?