I have a 07 street bob and was wanting to know exactly what the voltage regulator does....
The voltage regulator actually does 2 major jobs. The 1st job: Since the output voltage level of the stator windings is dependent on the velocity or speed of the permanent magnets, the output voltage level of the stator is dependent on the RPM of the engine. Since we want to charge our battery to a specific level or voltage we must "regulate" or control the output of the stator to a relatively flat voltage level. A lead acid battery has a nominal output voltage of 2.1 volts. What we call a "battery" is actually 6 small batteries in series. It is 6 cells X 2.1 volts or 12.6 volts. This battery likes to be charged with an electrical force of 13.8 volts.
The stator in the bike has a native unregulated output of something between 0 volts (0 RPM) to maybe 25 volts (4000 RPM). It may even be higher, because I have never checked it. The "Regulator" regulates the output of the stator to more or less the 13.8 volts that the entire electrical system was to designed to run at.
The 2nd Job:
The output of the stator is an AC voltage which can not be used to charge a DC battery. The negative component of the AC output must be sliced off and sent to the Negative terminal of the battery. The postive component of the AC stator must be sliced off and sent only to the postive terminal of the battery. Solid state Rectifiers are used to perform this operation. The rectifiers that do this, happen to be enclosed inside the voltage regulator case. Even though the rectifiers really have nothing to do with voltage regulation, they are packaged together with the Voltage regulator.
So even though your voltage regulator may be Good, you can have a blown rectifier which will require you to replace the voltage regulator unit. Actually the voltage regulator should have been called a Regulator/Bridge assembly instead of just a voltage regulator because it does both.
By its very nature, voltage regulation & voltage rectification will generate lots of heat. That is why you see
voltage regulator/rectifiers with large heat fins on them. Not being able to get rid of rectification heat is what kills most units.
Hope this helps, Hoople
