Lofty

Anyone have any idea how I convert my old Merc. 4 wire over to a 2 wire system? I have older Motorola Alternators and want to change over the newer style.

Thanks in advance guys.

Gary Anderson

Is your wiring harness set up for a 4 wire alternator, and you now want to use a 2 wire alternator?
Gary

Lofty

That's it Gary, that's exactly what I've got.

Gary Anderson

Simple. Connect the large (8 or 10g.) orange or red wire to the + post of the new alternator. The large black wire can go to the alternator body ground, - post (if it has one), or the block. The remaining 2 small (14 or 16g.) wires, purple and red, are not used. Be sure to cap these off so they dont short out. They still carry voltage.
Gary

Lofty

Dammmm!!! Too simple for my little brain. Thanks Gary. The purple and red are excitation, for what? I was looking at the schematic but just couldn't figure it out.

Lofty

One more thing. Can you go the other way? I have harnesses for 2 wire units but I've never tried using them.

Gary Anderson

Red is sensor, purple is excitation (switched ignition). You can use a 4 wire alternator on a 2 wire harness by attaching the sensor terminal directly to the + alt output. But you still need a wire to the ignition (purple) for the excitation terminal. That can go directly to the + terminal of the coil on a Tbolt IV.
Gary

Lofty

Gary, Thanks again, you've been a great help.