I have just recently been able to buy a Fulvia 3 from 1976 and have driven around 400 km since becoming the new owner. I do love this beautiful car, but after todays drive, I did have a question regrading some electrical symptoms (please bear in mind that I have never worked much on a car, so my knowledge is rather simple):
During the first times I have driven the car, I noticed that the alternator light sometimes came on right after engine start an stayed on for a short period of time. Usually this was only for a few seconds an disappeared latest when running the engine a higher revs than idle. The light did not come back after that, even when the engine was idling.
On todays drive I noticed that after around 15-20 km the light came on at regular highway speeds an RPMs. I was able to drive back home, with the light disappearing very occasionally, but the battery was discharged to some extent. Back home, it provided some residual power for the interior lights, but not for something like the starter. I did take the battery out to be able to recharge it with a car batter charger back home, but noticed that it has a "magic eye", that indicates the condition of the battery with green (everything ok), white (recharge battery) and red (replace battery). Mine is showing red.
Now my question, before I take the car to a mechanic:
- Can a defective battery be the cause of the alternator light coming on? Should I install a new battery and check if the alternator light still comes back on?
-Or is it possible/likely that the alternator or regulator is defective and actually damaged the battery?
Any other ideas or hints on what could be the reason and how I can troubleshoot?
There are some other issues with the car, but I'll open a different topic for this

Than you very much for any help!