Birdseye,

The "C" terminal must be connected to battery voltage as that is the controlling circuit on the system. If this is not connected, the alternator will be in uncontrolled voltage mode and fry the regulator/rectifier in very short order. Specifications call for no more than 0.2V difference between the "C" Terminal and the battery.

If a person looks at the schematic alone, it will leave a person with a lot of questions. Thoroughly review the section in the 912 series installation manual under "electrical system", "Technical data and connection of the electrical components", "Rectifier regulator", "Requirements for flawless operation of the rectifier-regulator". The text explains the function and proper connection of each wire.

A good starting point is to first decide what kind of cockpit indicator you want - idiot light, ammeter, voltmeter, ammeter/voltmeter and then go backwards - the problem with the schematic is that it shows wiring including all options. IMHO - the idiot light is worthless except for catching your attention (maybe) The ammeter is of limited value because it only tells you which way the current is flowing (to or from the battery). I went with a voltmeter because it will give a more comprehensive display of exactly what is happening with the system (over voltage, under voltage, proper normal operating voltage (should be around 14 v). The shunt is only needed with an ammeter. A voltmeter simply connects between the ground and bus. Deciding what indicator to have first permits a person to erase the un-needed connections.

Be careful with identifying the polarity of the capacitor too - those markings are quite cryptic on the capacitor too and a mis-step will cause an attention getting pop, smoke and a possible need for new shorts and a certain need of a new capacitor($).

I followed the above indicate rotax install procedures for our 912ULS and the system has worked flawlessly for 10 years sp far.

I don't have a photo of the connector - sorry.