[brucepick]

For what it's worth -
Either the "wht/grn" or the "wht/red" - or both - is/are part of the ELD system (electrical load detection) that controls whether the alt runs at approx 14V vs. reduced voltage of about 12.5V. I believe that ALTC controls the alt's operation. ALTFR sends a signal back to the ELD, from which the ELD determines how to control the alt via the ALTC wire.

You should test the black/yellow wire. Pull fuse #15 in the underdash fuse panel, which powers that wire. This fuse also supports the vehicle speed sensor (VSS) so you won't want to drive with the fuse pulled. BUT it's a fairly quick + easy test to do. If the alt is deactivated by pulling that fuse, you've identified a wire that will do the job. If it disables the alt, you could cut that wire at the alt. Or, you could install a switch and a fuse, in line with the fuse box. But if you use that method, you would need to power the VSS separately.

Consider getting a second wire with plug that will connect to the alternator. From a junker car. If you end up wanting to sever a wire at the alternator that extra piece of wire harness can make the job easier.

Yes, I've been thinking about this too. So far, that's my only achievement on this one.