i was given an S5 alternator, i've searched and found the wiring diagram, a great thread on the archives that show the step by step how to. but i do have one question, do you or do you NOT connect the (S) terminal to the (B) terminal. in the write up he connected it to the b, but later someone say that you'd be better off connecting it straight to the battery (+), so which one is it?

 

one of the wires goes to the b terminal while the other one can be connected to power the gauges and such like stock. I dont have time to check but here's the pix. Feel free to ID the wires

 

thanks, i already have the wiring taken care of, i just wanted to know if S needed to go to the battery, or to the B post. or if it mattered.

 

It shouldn't make any difference. The B post is connected directly to the battery.

 

that's what i was thinking, but i'm no electricist, and here's the thread i was going off from https://www.rx7club.com/1st-gen-archive-71/electrical-s5-89-alternator-install-into-1st-gen-528440/

 

On the FCs it runs back to the battery. It is a little better this way, but it doesn't make a real difference. When you connect to B, you are detecting voltage at the alt instead of the battery +. These should be close to the same. The difference comes especially during heavy loads or if your alt output wire and connection are not so great. The larger the current flow and/or the higer resistance of the output wire, the larger the difference is between the B terminal and battery +. This is why the S5s run this wire separately. This bypasses this issue. The sense wire does not draw much current and it is really sensing the true battery voltage instead of the alternator output voltage.

That being said, it is better to run it back to the battery + (add an inline fuse), but it can be connected to B without a problem. My S5 alt has it connected to B and it has been that way for several years without issue. I did upgrade my output wire to a new 8ga wire that I picked up from an audio store. This is a good idea to do. It makes no sense to upgrade the alt and use the old wiring and not be able to effectively get the extra potential current to the battery/car.

 

awesome, that makes sense, thanks for the replies and the clear up. . . guess i'm off to go plug some wires

 

what the amps on a s5 alternator

 

80, compared to the whooping 55 on the FB stock Alt.