912iS Battery Discharge.

Oh boy...you are in real trouble when you have someone working on the harness that has no knowledge of the system.  White wire are because they are aircraft Tefcel (150C rated) wires and not junk automotive wire.  If you can't understand the installation manual then you should not ever cut or splice any of that harness.  All I can say is best of luck, I would not know where to begin has someone hacked into that main harness.  

The engine has a split generator stator.  It starts on the large stator side (B) and at 2500 RPM it will excite the small side, (A).  A runs all the engine critical parts B after that point is to run the bus for your aircraft.  The pin out is shown in the installation manual and you can find additional information in the maintenance manual heavy.  

Cheers

This is a full copy of the technical diagrams for the wires.  The installation manual, IM, has all the relevant ones for correct installation.  You can download it at www.flyrotax.com 

Not sure I agree with your A&P. White wires are standard in Aircraft very very surprised your A&P does not know this. We have many Tecnams on the field they do not seem to have higher rate of issues with wiring cf others.

Some A&P are adverse to any wiring especially if the grew up with old GA aircraft which have virtually none !

Modern aircraft generally have a wiring harness which allows the users to add in other items as they wish.

The IS engine ...of course requires much more wiring it is more like a modern car engine, a lot of sensors, circuits and busses if you A&P does not have experience with this type of system then you might need to find another or send them on an appropriate Rotax course. Both Rotax and Tecnam are professional companies and know what they are doing generally if you THINK they are wrong actually it is a lack of understanding about the systems they are infact almost always correct !

Anyway just my experience

Jonathan wrote:

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.

You said ..."instead connect Gen B directly to the main battery somehow".

Although Gen B is in normal conditions chaging the main battery as one of the functions of the Fusebox, this is not always the case. Please follow the electrical wiring recommended on Rotax 912iS Install Manual. I've never had problems with installations done following that manual.

Maximo....the Rotax part of the wiring harness is standard aviation materials.  Coloured wires would indicate mil spec or automotive and not really suitable for this type of engine with CAN Aerospace protocol.  Any wires in the cockpit have to be temperature resistant to 150C and even mil spec wire is only good to 100C.  Tefzel wire, the white ones you see, are used to have the correct temperature resistance and will not emit toxic fumes if burnt. 

As a note, there is no charge to the battery until the B side generator comes online. 

Cheers 

Rotax Wizard, I'm not sure what you mean with respect to wire ratings.  Tefzel coated wire is MIL-SPEC.  MIL-W-22759/16 (often abbreviated M22759/16) wire is a multi-strand tinned copper wire coated with Ethylene Tetrafluoroethylene (ETFE, Tefzel) insulation that's rated for 600V and 150°C.  It's available in a wide selection of colors (see the attached chart); a color other than white doesn't mean that it has a lower temperature rating.

The basic part number is followed by two "dash numbers." The first number indicates wire gauge and the second, insulation color(s).

There are a few additional color codes that are fairly uncommon in the wild: P = pink, T = tan, D = dark (i.e. D6 = dark blue), L = light (i.e. L6 = light blue).

Striping is indicated by two color numbers: -90 would be white with black stripe.

Twisted pairs are sometimes called out by separating the conductor colors with a forward slash: -95/96 would be a twisted pair composed of white with green stripe and white with blue stripe.

So, MIL-W-22759/16-22-95/L60 is a twisted pair of 22AWG MIL-SPEC Tefzel-coated wires, one white with a green stripe and the other light blue with a black stripe.