From Citroen SM Wiki
The original regulator ...
- The metal cover can short out. Fit a fuse to the supply wire at the top of the regulator.
Incorrect charging may be the body of the regulator is not directly connected to the battery negative (O.E. is a yellow wire). High charging can be caused by a low voltage in the regulator supply wire. First check for bad contacts elsewhere.
There are a number of alternatives:
- Fit a Ford external regulator (e.g. 1982 Ford Mustang) "I,A,S,F" terminals of Ford Regulator go to wires "L, Bat, R and EXC" from Citroen Voltage Regulator. It is also possible to fit an aftermarket miniature Ford voltage regulator inside the OEM regulator can.
- You can also mount a modern alternator with internal regulator, such as a Delco CS-121 alternator from a Toyota/PontiacLeMans.
- http://www.candokaraoke.com/Regulator.pdf -- Citroen DS voltage regulator adapted to maintain BVH starter interlock.