Alternator question, battery is discharging quickly.

[TitaniumTT]

Originally Posted by RETed

1) The 12VDC reference wire (which you call a "pin") needs to be connected to +12VDC constant, direct to the battery.
This is applicable to the FD and Kouki FC alternator circuits; prior to that, the Zenki FC alternators were only wired to switched +12VDC.

As odd as it is, I have close to zero experience with the S4 stuff as I never had any problems with the S4 alt because everything was virtually stock. It wasn't until I upgraded to the FD Alt that I started having issues. Much like you Ted, when I started with the FD alt, it was rebuilt by IRP and never worked right, I too blamed a shitty reman, although as it turns out, that probably wasn't the problem

Regardless, in this case with Zac, he's running an FD Alt and it needs to be connected straight to the battery, not a switched source as is already there, so that is definitely problem 1 in Zac's case

Originally Posted by RETed

This tells the alternator what the status of your battery is.
Try not to connect it to the +12V post off the alternator, cause it'll be higher than the battery + post, and there's chance that you get back EMI from the alternator operation - this is why you don't see the OEM's wire it to there, even though it's a short shot.

The EMI I hadn't thought of, that's a valid point. In all the searching when I was having all of my issues, the general consensus as to why that singular wire is run back to the battery is because we're altering the output of the alternator based on what that sense wire is telling us. Just because it's 14.4V at the charging post, doesn't mean that it's 14.4V at the battery and that can be due to a variety of reasons.

Originally Posted by RETed

2) The other pin is for the idiot light.
Like others who have already said, it's not necessary to connect this to anything.
This just completes a circuit (to ground?) so your idiots lights light up when the alternator fails.

This is where I disagree. This could very well be the case for the S4 alts but it is NOT the case for the S5/S6 alts. The later years NEED the idiot light pin to be hot when the key is on and the alt is spinning. If not, it will die an agonizing death.

Again, I don't have the knowledge of the S4 alts just because I NEVER had a problem with mine because stock, but when I did the Cosmo swap and the S6 alt upgrade, I had issues for about 5 years... literally... because I was only running one switched wire to the alt. The death was always the same, it would start overcharging and eventually kill itself and the battery.
Also, with only the one wire for the alternator connected to a key hot, when the ign switch is off, the Alt would kill the battery in a matter of days.
Again, much like you, Ted, I solved that problem by flipping the breaker everytime I got out of the car - NBD

Originally Posted by RETed

As for your problem...
I had the old silverrotor FD alternator, and it always had a major drain with the engine off.
I bandaided the situation by resetting my circuit breaker anytime I left the car off overnight.
I traced the problem to the alternator sense field not dropping even after turning the ignition key off; for some reason when I dropped the +12V reference, this would drop the field and killed the excess current draw immediately.
I just chalked it up to a crap rebuild (these things were rebuilt by silverrotor by some shop).

Once I replaced with another unit, I NEVER had that problem anymore.

It sounds like it was a bad alt and it was pulling through the relay/idiot light and keeping the alt energized which would quickly kill a battery.

The "Sense" wire, the S wire, in the S5/6 is connected straight to the battery. It senses the voltage and adjusts the output of the alt to attempt to feed the battery the needed 14v. On the S4's it's called the R terminal, and that gets fed to the B/W wire which is hot when the key is in any position other than off.

Both the "L" Terminals on the surface accomplish the same thing. They illuminate the idiot light when there is a problem. However, as far as the alt is concerned they accomplish very different things and it can be seen in the wiring diagrams.

The S4 has a diode on the relay that only allows current to travel one way. When the alt goes bad, or is not charging, the W/B wire latches to ground, which energizes the coil, which closes the circuit in the relay to ground and with the other side of the idiot light connected the B/Y wire (also key hot) the light illuminates. It appears to me that the S4 alts can be run with only a single wire and run properly and as designed (meaning they won't die quickly) by leaving the idiot light wire left unhooked. Regarding the S4's, the L wire is an output, not an input as it is on the S5/6's

Originally Posted by RETed

So it's quite possible you're in a similar situation.

It could be possible that you have a shorted diode in the rectifier, which would cause the alternator to keep draining voltage with the engine off too.
I've fought this problem with my MX83 alternator, because I think the 15VDC+ levels my battery charger was giving it when I had to jump it.
In this situation, every time you reconnected the alternator, the current draw would always be too high.

It's very easy to troubleshoot these things, as you need someone to measure current - most DMM's do this.


-Ted

The diode is most likely blown on Zac's car because it's an S6 alt.

Originally Posted by FC Zach

Pin/Terminal. . . whatever, you know what was being referenced. But yeah, I am redoing the wiring now.

That's what I thought too but is contradicting to what others have said. Some say it has to be connected and others say not necessary. .

Let me state this as fact, because I've fought these issues and anyone running an S5/6 alt on an S4 car is going to run into these problems and I can say with certainty that you need to have both wires connected and working properly for the S5/6 alts to live a decent life ... TRUST ME!

Originally Posted by FC Zach

I'm afraid I will still have some sort of issue even after making the proper connections. . . I drove for far too long without the 12v reference wire connected. I added new leads to the connector, now to make the connections once I find the easiest/best route to take.
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Zac, right now, or rather before we started chatting, you only had one wire connected to the alt. How was that wire run and is it constant hot? ACC only? Acc and start and run? If it's a factory S4 B/W wire, that will work fine, you just need to add the resistor that we talked about. Then the S lead can run straight to your battery and it'll work fine, assuming it's not already fucocked.

[FC Zach]

Originally Posted by TitaniumTT

Zac, right now, or rather before we started chatting, you only had one wire connected to the alt. How was that wire run and is it constant hot? ACC only? Acc and start and run? If it's a factory S4 B/W wire, that will work fine, you just need to add the resistor that we talked about. Then the S lead can run straight to your battery and it'll work fine, assuming it's not already fucocked.

Up until recently I had only the main battery charge cable ran but in the past, I had a lead running to a switched 12v source I found on the driver side strut tower in a vacant connector attached to the fuse box bracket. Where I had the opposite end of that lead going? ? ? I don't remember but I think I had it on the "L Terminal" so if that's the case, I've never had a reference from the battery connected to the "S Terminal".

What I'd like to do is find the old alternator wires or the connector/harness they would have come from and wire my leads there. . . wherever that is.