I have the FD alternator and I've been running it for about a month now. But I don't have the S Terminal hooked up and I'm reading voltage on the Dash. The L terminal being shown I do not have hooked up at all. I have a s4 body, where is the location of the dash wire and If I cannot locate the dash wire where do I need to run this wire too?

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Refer to the attached schematics. You can see that the only difference between S4 and S5/6 alternator wiring is that the S4 alternator has an R terminal fed ignition-switched power and the S5/6 alternators have an S terminal fed constant battery power. The rest is the same.

The best way to wire an S5/6 alternator into an S4 is to simply replicate the S5/6 wiring by running a wire from the EGI fuse (white/blue wire) to the S terminal. (The lazy way to do it is to feed the S terminal directly from the B terminal, but if this was the best way that's what Mazda would've done.) The white/black wire should be connected to the L terminal as it was before and the black/white wire should be cut back and insulated (it's live when the car's running).