arsinal4496

iTrader: (10)

Im goning to start swaping a S4 tii engine into a s5 n/a harness/chasis in the near future. Im going stand alone so most of the engine harness I wont use. My questions lie in the alternator wiring. Iv searched and found the wiring diagram, posted in sevral threads, below. Reason for doing this is because the s4 alternator on my turbo engine is new, so id rather use that one.

The “B” terminal simply gets bolted on to the s4 alternator and the “L” (dash) terminal wire will be sodered to the “L” wire on the s5 harness.

1. what is done with the “S” terminal wire in the s5 engine harness? Can it simply be covered/taped away? Or should I join it with the “B” terminal possibly?

2. whats the best switched wire you guys have used? I know theres a switched wire in the green connector by the drivers head light, will that work?

I typed all this while im doing 3 different things at work, so if some stuff doesnt make sense bare with me. Any help is always appreciated, and I did search!!! ….just want to be absolutely sure about this and not fry anything or drain my battery either.


Thanks!!!

jackhild59

iTrader: (7)

That S4 alternator is pretty low output by today's standards. You should really move up to something else. Now that I said that, here is the answer to your question.

The 'S' Terminal senses voltage at the main fuse block. This is the 'sensor' wire that gives the voltage regulator feedback so that the voltage is maintained.

Now the voltage is maintained to roughly 14.1 volts at wherever the 'S' wire is attached. Attach it to your 'B' Terminal and you have a setup like a 1-wire alternator. It will work and is simple, but your battery will never see 14.1 volts if you do that.

I would advise going to the main fuse block or to the + terminal on the battery. This attachment will allow the voltage regulator to maintain the 14.1 volts at your battery. If you go to the battery you need to fuse it for safety. 10 amp or 5 amp will do. If you go to the fuse box, well it will be already fused.

Good Luck

arsinal4496

iTrader: (10)

ur very right about the s4 alternator being outa date. i expierenced it my self once i installed my gauges and stereo in my old fc. everything got really dim, plus i think the alternator was on its way out too. so i got it rebuilt to a higher output alternator, so technically i guess it isnt spankin new but it outputs 110 amps

and thanks for the help, ill attach the "s" wire to the battery post i have in the engine bay. my battery sits behind the passenger right now. and i have a few fuses and fuse holders laying around too.

any ideas on a good switched wire?

jackhild59

iTrader: (7)

Ok, you might have missed the principle of the S wire. It is even more important with a remote battery to take the S wire to the battery. There will be voltage drop to that remote location, more than you want. If the sensor wire is sensing voltage, it should be at the remote battery.

arsinal4496

iTrader: (10)

ahh, u know what i was thinking about that as i posted my last post, since ur right, there is a voltage drop between the battery and the post. ill just run a wire straight to the battery.... excuse my nooobness, but if i were to just wire to the fuse box, how would i go about that? or i could even search for it, i just wouldnt know what exactly to search for.