I have an s5 alternator on my s4 TII and I noticed that only the B terminal has a wire coming from it, there is nothing coming from the L and S terminals. The weird thing to me is that the alternator still charges the car's battery, but only above ~2k rpm.

 

The two wires on the back are for power to the internal regulator and to provide field voltage for excitation. BUT a alternator will self excite itself thru residual magnatism in the rotor IF you rev the engine high enough. Then it'll put out voltage til the engine is shut off.

Problem with that is, there is no regulation of the output voltage and voltage output seen AT the alternator over 15vdc can harm the electrical circuit of the car/battery.

You NEED to provide a constant source of power to the pin in the back that is on the left. It needs to be power that is there 24/7 days a week. The pin on the right can be attached to the WHITE/BLACK wire on the original series four harness plug. NOT to the BLACK/WHITE wire though. The BLACK/WHITE will not be used at all. That wire is switched batt voltage and will not do the job on a series five/six alternator.

 

Ah I see. So from what I understood from some alternator write ups on this forum is that I don't really need to hook up anything to that right pin, only the left one for the regulator. Is that correct? Also, if I have this s5 alternator all wired up properly, I don't have to change anything when putting an s6 alt on?

 

I've never messed with S6 so I'll leave that alone. Just the pin on the left in the jpg needs constant batt voltage 24/7.