Please help with alternator wiring

[KiloWhiskey1]

I'm helping a friend sort out a low voltage problem on his RV-10. He is just out of phase 1 and the alternator has persistently only charged the system to between 11.8 and 12.2 volts. The plane uses a VPX electrical system and a Nippon Denso alternator. I don't have the paperwork or wiring diagram for the alternator.

Can someone please tell me what the red, green, and blue wire to the alternator plug should be connected to?

Thanks very much! Keith
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[Geeman]

http://www.vansairforce.com/communit...d.php?t=114652

[Neal@F14]

Nippon Denso alternator 3-wire plugs are usually:

Green = ignition (+12v from field breaker)
Red = warning lamp
Blue = either "sense" or "dummy" depending on the particular alternator

Most of the time the green one is all that's really needed and the red and blue can be left unconnected.

[KiloWhiskey1]

Thanks Kyle and Neal!

I'll try the green wire tomorrow and report back. It is unconnected at present, so I'm hoping the solution will be this simple.

Keith

[KiloWhiskey1]

Just wanted to report back that my buddy's RV-10 is now getting a steady supply of 13.8 volts from it's Alternator. Originally the alt field breaker was wired to the red wire of the Nippon Denso alternator and under this configuration it would only push around 12 volts. With Neal's wiring description, I switched the alt field to the green wire and the problem was solved.

One amazing additional observation was that the airplane was a full 12 knots faster on the 1st test flight after the wiring change. Anyone want to venture to guess why?

Thanks again for the tremendous help!

Keith

[rv7charlie]

That's a pretty big change, but assuming nothing else changed...
Electronic ignition with improved spark from higher voltage?

[walkman]

I get 14.2v from the sale alternator, which is what it showed on the test strip it came with from NAPA.

Why 13.8 on yours? I would expect more like 13.3 or 4 if you are picking up voltage on the other side of an e-buss diode (roughly .8v drop). So, it seems its either low or high depending on if a diode is in the system

[KiloWhiskey1]

Not sure why the 13.8 vs 14.2. I didn't build it and don't recall if he has diodes installed. I was pretty happy just seeing it charge.

Keith