Hi , so it was a bad diode the main cause of the red light on when the ignition was off ?
I had the opposite situation , I had a very dim red light on when the blower fan or radio were on at the same time . The voltage was jumping around from 14 to 16 at idle . I have replaced the voltage regulator with a new beru and the problem was solved .
My mechanic removed and checked the alternator and is ok and charging properly but probably some diodes are defective too .
Should I expect to have the same problems as you ?
When the key is off and the red light is on , it means there is a + on that bulb somewhere . Where this + comes from ??