alternator wiring connectios

I haven't done it but have heard from many knowledgeable sources that the way you propose to do it is correct. One field connection to grn wire and ground the other. Alot of times when a circuit is open there will be residual voltage that can be measured with a voltmeter. That may be what your seeing. To play it safe you could get a fuse holder with a 2 or 3 amp fuse and ground the extra field through it for a test. I don't believe the field carries much current so it shouldn't blow the fuse if all is ok. If the fuse pops then it might be a problem. If it works you can eliminate the fuse and directly ground it.