To start this off I HAVE searched and well, every explanation just doesnt seem very clear to me. Either it's my problem and I can't understand that wording or it is in fact not clear. In either case I just have a quick question.
Here is the diagram:

I've got an FD alternator with a dual belt pully and a red top optima battery on my 87 TII
The battery keeps getting drained and the car won't start. It usually takes about 2 weeks every time I get it charged for it to do this and the shop says both the battery and the alternator test out fine. I'm assuming its the wiring now. This is how I've wired it:

Terminal S wired into the Black wire/white stripe
Terminal L is wired into the white wire / black stripe
Terminal B is wired to the terminal B from my S4 alt.

I'm assuming I wired terminal S wrong and that I need to shrink wrap the end of the black wire/ white stripe and re-wire terminal S to a 12v power source.
Is this right?
And if it is where should I wire it to? Which 12v power source exactly? Do I need a relay or anything? If its any 12v power source couldn't I just wire it up to the wire coming from B terminal?

Thanks

P.S. Why doesn't the black wire/ white stripe work as a 12v power source/ It's switched by the ignition so that it supplies 12 volts when the key is on just like a relay would... or does the internal circuitry of the alt require that it gets 12v even when the car is off?

 

Terminal S needs to see constant 12V. Any 12V constant source will do. You can follow the wire to the engine bay fuse box and make your 12V connection there.

The w/b wire is switched 12V. The regulator in the alternator needs constant 12V or you get the battery discharging to ground through it.

 

Thanks, you've no idea how many people I've asked.

 

Zack, for the FD alt, you put the B and S terminals to a direct 12v source? i am thinking i will run it str8 to the battery post. and last terminal L goes to the bottom end of the T shape connector of the S4 old alt output?