911 2.7 charging problem
 

can anyone help?
my car starts fine, battery light goes out, about 20 mins later the battery light stays on until about 2200rpm at no stage does the alternator light come on or even flicker, i had the alternator reconditioned and the engineer said it was charging well on his bench, i checked with a meter it is only reading 11.8v at tick over increasing to 12.9v at 3000rpm.

Your voltages look too small. You should be getting more voltage out of the alternator. You could have a couple of diodes going bad.

What year is your car? Do you still have the external voltage regulator?

its a 1975 with a external regulator and had one diode replaced when sent for repair

general rule of thumb

always replace external regulator when rebuilding alternator

ttt

ttt

Yup, there is your problem (most likley). The regulator does just that, regulates voltage. Try that and see what it does.

i will give that a try