Upgrading to S5 Alt what gauge wire do i use for terminal S?
 

Wassup yall my alt took a dump on me so im now in the process of switching to an S5 alt. Ive searched but no luck really. Just curious as to which gauge wire i use to connect from the battery to fusuble link to terminal S. The plug wire isnt that big so im confuse that some use such big gauges. Also for Terminal B should i put a big gauge wire direct from the battery as well or will the stock on hold up?

The 'S' wire size is irrelevant. You can use the stock harness wire.

For the 'B' wire, you *can* use the stock harness. There is talk (unverified in my opinion) that the stock wire has a crimp that becomes corroded and causes problems. In the stock harness that wire goes from the alternator to the starter then back to the main under hood fuse block. The battery positive also connects to the starter.

So you can unwrap the stock harness and replace that wire with an 4 gauge (some say 2 gauge) wire.

Or you can do as I have done on my 88 TII and ADD a second heavy wire from the 'B' terminal of the alternator to the battery. You should fuse this wire 60 to 80 amp fuse as close to the battery as possible. I used an 80 amp Megafuse a couple of inches from the battery end of the wire. I used the main charging wire from a Ford Taurus for the wire, 4 gauge. I crimped and soldered the original 'B' wire and the Taurus wire together at the terminal that connected to the alternator.

After doing this extra work, I could tell no difference in the performance of my charging and starting system. Full disclosure, I have a large frame 3G Ford alternator on both my 88TII and my 90 Vert. The 90 Vert uses all the oem wiring from the s5 alternator install. The 90 Vert 'B' wire is substantially larger than the 88 TII wire.

Good Luck!

Thank you for the info. I might just go the route you went and add a 4 gauge with a fuse. a 30 amp would be enough right? s4 alt is just poops ive driven an s4s with s5 alt and its better in every way and thats only 10 amp difference maybe your just used to the big ford alt already.

I got along fine in my Vert with the S5 alternator. I ran an aftermarket head unit and a self powered Bazooka sub. Then, I went apesh*t over Efans. I currently run a Lincoln Mark VIII 18" 2-speed cooling fan. Low speed pulls 15 amps-and activates at 195* on temperature rise. It pulls 25 amps on high speed which activates on A/C compressor operation. That was too much for the S5 alternator to handle. So I upgraded my alternator to a large frame Ford 3G alternator supplying 130 amps. All oem S5 wiring.

S4 alternator is a different animal which I cannot figure out. On two different S4's I have not been able to get the voltage up to spec regardless of what I did. They always put out low volts (12.5 to 13.2 max) regardless of the load. One was an S4 N/A that had weak oem alternator. Replaced it with an S5 alt and it was golden. I used all oem wiring except had to make the change regarding the S5 wiring requirements. Do you have the diagram to make the S4 to S5 changes?

yes ive searched it up apparently you just have to excite one of the wire on the plug of the s5 alt directly from the battery to a fuse if there is no fuse then the car will try to recharge even when the ignition is off. I think im just gonna try out an FD alt only problem is finding a pulley now.

https://www.rx7club.com/2nd-generati...tor-fc-912434/

I did an IR Performance FC alternator, 130 amps. Sent in my s4 core, came back within a week. No rewiring, no swapping pulleys, no nonsense. Same basic setup as what they've had excellent luck with on the FD's. I highly recommend PM'ing him.

does sound like a win win how much did that cost you? Whats the voltage reading after the upgraded alt?

It is quite expensive at $230. However, the guts have been tested on the FD's and proven to put out sufficient current even at idle. All the leg work is done, so for me that piece of mind was worth the cost. Honestly I didn't even bother checking the voltage yet, we needed to race and just slapped it in and left. No problems since.

Don't do this. Rewound alternators and their inherent problems are a re-current theme winding their way through threads like this.

The physics just don't work. There is only so much space in your S4 alternator case.
Rewinders increase the wire size of the windings to increase the amperage output. Problem is that with the wire size increase, you cannot get as many wraps of the wire inside the case. This causes the voltage at a given speed to be lower. Not might cause- DOES CAUSE. The only solution is increase the alternator rpm.

Rewinds might work fine in a racecar. They will work fine at highway speeds. They WILL put out low volts at idle and low rpm driving where you spend most of your time. All decent rewinders will advise you that this is the reality. The typical rewind uses a smaller pulley that will spin the alternator faster.