The regulator slash rectifier performs two tasks. Power coming out of
your Rotax engine is AC power. The two yellow black wires coming from your
magneto each have a different "phase". The regulator/rectifier converts
this from a 3 phase AC power to a single phase DC.
The magneto is always trying to put out the same amount of power, this
creates a problem when the battery is fully charged, or there is no heavy
load on the system. A lot like a tap filling a pail of water, if something
is drawing water from the pail at the same rate it is entering it will not
over flow. But if the water keeps coming in with none being taken out, it
will over fill, - thus the battery over charges.
The regulator rectifier prevents this by taking the excess voltage and
and converting it to heat to keep the system with acceptable limits.
For the system to work properly, the ground on the plane MUST be good.
If the ground is poor the charge that would normally be going into the
battery, now goes into the rectifier and possibly other electrical
components connected into the system. This of course can cause failure of
For this reason it is imperative that all grounds be checked for
corrosion. This can be caused by copper wire connected to a steel
airframe, two dissimilar metals will act on each other, add rain, battery
acid, vibration and you have copper sulfate which is that blue powder you
find on your battery terminals.
The battery is 12 volts DC - and is being charged by the use of the
regulator/rectifier it's purpose in the system to to provide a "sink" for
the system, reserve power when the engine is at an idle, and a power
source for starting and operating equipment when the engine is not
How to check your regulator
rectifier in pdf format
Rectifier Wiring diagrams
Rotax offers two rectifiers for their two stroke engines