Some final notes on these mechanical regulators for people needing to change out the solenoids. You can, and I have, replaced the light solenoid with a standard 12V solenoid coil. Technically, this coil should be more of 6V coil solenoid because it operates at half the nominal system voltage off the N wire. The other coil (field solenoid) will be more sensitive to proper selection. A standard coil could be used as a direct replacement, but what currently occupies the 10 ohm place in the circuit will need to replaced (or added to) with a value which brings the solenoid coil resistance to a value which causes the charge out put to be within spec. A potentiometer would be the best as this will allow some adjustment of the charge voltage to obtain around 14-14.5V.