Can you explain why, CS?
The coils are supposed to be totally insulated from all points of the chassis, engine and everything else. The coils are still separated from the rest when the reg/rec is connected by the diodes in the reg/rec which only allow current to pass one way. To negate a defective diode giving a false reading it is recommended to always check for voltage between the coils and earth with the reg/rec disconnected.
The coils are supposed to be totally insulated from all points of the chassis, engine and everything else. The coils are still separated from the rest when the reg/rec is connected by the diodes in the reg/rec which only allow current to pass one way. To negate a defective diode giving a false reading it is recommended to always check for voltage between the coils and earth with the reg/rec disconnected.