I have a Bosch Alternator that has a fault in the charging circuit
I intend to wire a relay to give the Field a voltage reference when the car is running
Do I need a bulb in the circuit to drop the Battery/Reference voltage, keeping an offset between the Field, and Battery ..???

Model, year would be good to add to you post and your signature

Welcome to the forum

__________________
1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

typical 2 wire bosch alternators with internal regulator require a 3W bulb on the D port with a live on the other side of the bulb, otherwise the alternator wont start or umm excite.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

1990 Merc SE300
the Alternator charging circuit is nearly the same for all Bosch

3w .. could be a
"1024" then ..

thanks ...!!