912iS Battery Discharge.

Try to turn the G3X backup battery on.

My aircraft has almost identical airframe electrical loads and it runs a little over 11 amps.  It looks to me like what your gauges are telling you is correct. You are using 11 amps, 10 being supplied by the alternator and 1 being supplied by the battery.  At 5000 RPM the internal alternator on the 912iS should be able to provide over 25 amps, so something is wrong.  I have seen partial failures like this on the 912iS.  Alternator B, regulator B and the wiring between should be inspected and tested. 

It's possible that one phase of the 3-phase stator isn't reaching the regulator due to a connector problem or a dead diode in the regulator's rectifier.  Either one would reduce the system to single-phase operation and greatly reduce its output capability.

A damaged rectifier diode is difficult to test in a fully potted regulator, but you can check for a shorted diode.  With your multimeter in diode check mode, test each of the pin pairs (1-2, 1-3, 2-3) of the regulator connector in both directions.  You should get no meter response (open circuit on all tests).  If your meter does detect a diode (voltage drop of around 0.7V), then there's a shorted diode in the rectifier.

Unfortunately, success on that test doesn't necessarily mean that the rectifier is undamaged.  If a diode is blown open, it will test the same as a good rectifier.  You would have to substitute a known-good regulator to determine if yours is faulty.

Check the stator-to-regulator harness connectors for contacts that aren't seated all the way into their connector housings.  Make sure the connector plug is fully seated into its receptacle.  Look for connectors that show heat damage.

If you find a heat-damaged connector, and its housing is rectangular and made of grey plastic, then it's possible that your engine did not have SI-912i-024 performed.  This SI calls for replacing the factory-installed stator harness connectors (Deutsch DT parts; rated for 13A per contact) with a more robust alternative (Amphenol ecomate RM: round, metal, twist-lock, 45A per contact).  The replacement connectors are available as a kit from Rotax parts dealers (part number 481510, $458).  They require specific and expensive tooling to crimp their contacts (see here and here -OR- here and here).  The connector parts are available from Mouser for $71 (here).

If your aircraft is Experimental and you're able to use an alternative method to comply with the SI, then consider using Amphenol ATP connectors instead.  They're very low cost and are rated for 25A per contact, which is more than adequate for this application.  See this parts list for everything you'll need.  Buy a couple of extra pins to practice crimping with.

The genuine Amphenol crimper for this connector's contacts is the last item in the parts list.  If you want to save $12, there's a good quality crimper available on Amazon (Iwiss / iCrimp IWD-12).

Hi Eric & Jeff,

Many thanks for analysis and suggestions which have helped me better understand my new 912iS Engine.

Eric great info thanks.

I will do the checks you suggest plus ask about SB SI-912i-024?

Will talk to the  Rotax Distributor here in Australia  tomorrow about my situation.

I will report back  the outcome to this.

Thanks

Lance

Lance, get ready for a world of electrical problem pain with your Tecnam. I have one, too, and as I've come to find is the case with all Tecnams, your electrical problems will be ongoing forever. On mine, for reasons I don't understand, my battery voltage suddenly would never go above 12.6 with the engine on, even after I spun up Gen B (by increasing power above 2400rpm for a few seconds). My A&P was baffled by the wiring going into the firewall as it didn't make any sense to him so he decided to just splice out the connection going into the panel and instead connect Gen B directly to the main battery somehow. Or something like that. I'm not really sure. All I know is that after he did whatever he did, I now get 13.4-13.6 volts immediately after spinning up Gen B. Which is what it should be. But what I lost was my annmeter. It just always read 0 after that. So I removed the graphical display from the EMS after having a long conversation with my A&P about it because on an airplane this simple with so few electrical loads it doesn't really matter much anyway seeing the amperage charge/discharge. I would just know that Gen B has failed if my battery voltage dropped below 13 in flight. So I don't have an annmeter anymore, but hey, at least my battery is getting fully charged in flight whereas it was only receiving a partial charge before my A&P did whatever re-wiring he did! 

Unfortunately, nothing about the way Tecnam does their electrical wiring makes any sense. My A&P has commented time and time again that Tecnam's wiring is garbage, ALL the wires are white and not color coded, and there are tons of wires that go nowhere, there for no purpose, and lots of other wires that are irrelevantly routed places. Tecnam's wiring is just a mess. AND Tecnam fails to install anti-chaffing protection on a lot of their wiring, which is a huge safety issue. I've had grounding problems as a result.