Alternator question, battery is discharging quickly.
 

For a while until this Monday, I have been dealing with some mystery drain to my battery. I found it by accident while detailing the engine bay where I heard a faint electrical whine that seemed to come from the alternator which stopped after removing the battery lead.

Before finding this issue, I'd have to keep a trickle charger connected to the battery or else it would completely drain within a couple weeks. It was attached when I found this problem. I left the lead off the alternator and disconnected the charger and left alone for a few days.

After giving it a few days with the charger and alternator disconnected, I reattached the charger to see if it would attempt charging the battery but it didn't. It was fully charged so I can confidently say it was the alternator.

Details:
-'87 RX7
-3rd Gen Alternator
-The 2 pin connection on the alternator is vacant
-Battery is good, tested. Tried another in case.

My questions:
-Does the two pin connector need to be connected to the alternator?
-If it's not a bad alternator (going to test it soon), any recommendations on what to check next?

One of the pins on the alternator needs to be connected.

Noob.

It used to be connected. . When researching about it years ago I was under the impression that it was a redundant connection. So. . some time ago, about the time I converted it to EFI, I removed that connector to clean things up.

Since it's been a while since I've done this, I do not remember where that wire goes. Is it switched or constant 12v?

With that being said and before it's mentioned. . I never made the connection of the two because I thought the drain was related to the Haltec wiring and not this little single wire connection.

I believe switched. The main power wire is of course constant.

Sweet. . but what change would it have in my case if that connection is switched 12v?

When I connect the bottom pin to the battery lead on the alternator, the whine goes away.

One of the pins needs to be connected to the battery, or a constant 12v+ source. The other pin pulls current through the idiot light. If both of these aren't connected, it will drain.

If you only have ONE wire run to the Alternator, you can use a resistor to mimic the difference in current at the alternator.

Could I simply do this, connect here?

https://c1.staticflickr.com/3/2909/3...6e1e0db9_c.jpg

Sounds like the bottom pin goes to the battery, the top pin goes through the idiot light.... oh, that pin needs to be keyed as well

I've never had the top wire (the empty spot in the connector) connected to anything. Is that recommended?

You could, and you could use a resistor to connect to the top pin, however the top pin needs to be keyed or you'll get the same drain

It's necessary to keep the alt from draining the battery, unless you do a complete battery disco, which I usually do anyway because Rotary.

Ok cool, thanks guys!

One problem though. . I don't remember but does this connector have the "idiot light" wire you speak of?

Yes, one wire is straight to the battery, the other pulls through the idiot light.

Oops, forgot to attach pic. . Can the to wire be connected to this, do you know off the top of your head?

http://rotarycarclub.com/rotary_foru...0&d=1487864599

Just checked the manual and the my OE plug would have been a small T shaped connector. Mine is not there. oh well, I'll have to figure something out.

That looks like the CAS wiring and if that's still there, you might be able to use those wires to power the ALT, with come retasking of course

S4's use the T-shaped connector, S5+ use the style that you're using.

What happened to the T connector?

When I went carb, I removed the harness.

Yes, however that plug is on the driver side POWER harness, not the ECU harness. The CAS is also on the power harness, which you clearly still have.

It's there somewhere....

Ah. Ok, so heres what you need to do.....

Buy Scotch
Buy plane ticket
??????
Profit

Butt seriously, depending on how much of the harness you cut back or removes, and I think I know which harness you pulled out ... Giggitty ... you need to go back to the FE-03 connector, between the "Front" & "Engine" harness and find the B/W & W/B wires and run them up to the alternator and plug them in. That will do it.

If the FE-03 connector isn't around anymore, you can get them on the FEM-01 plug and route them up to the Alternator. That plug is or course located around the stock ECU.

Now, if you've already got a nice Ludwig Harness and you don't have the provisions in that harness for the Alternator, what you can do is use the vacant CAS wiring that you showed the pic of. Those will be in the Front Harness and routed over to where the ECU lives. From there it's a matter of jumping the wires from the FEW-01 plug to the CAS wires (R,W,L,G) and then making the connection to the Alt.

Any of those approaches will properly control the Alt and prevent battery drain. But the key is, regardless of what the internet says, or the GM crowd, the alt NEEDS both wires to work properly and not kill the battery either by slow discharging death, or 16V overcharging death

Where I'm at so far.

https://c1.staticflickr.com/4/3860/3...5ac51923_c.jpg

Going to connect the top to a switched 12v source but need a resistor?

It's not there.

Do you have my number?
Are you off today doing this shit now?

I'm a night shifter, been at this for a while now.

No number.

I have sweet Brian's number....

He's got you blocked and has a restraining order against you :)

^ :smilielol5:
DJ, you want haz play matchmaker?

Hey Zac, remember what I said about the 7club being all fuuucocked? Well..... yeah... Check this out,,, ignore 7Dust, he was handed the answer 3 times I counted, he's a fucking stubborn idiot... I dunno what it does, so I'm gonna leave it unhooked. I don't care about idiot lights, so I;m going to leave it unhooked. There's the problem

Satch & RockLobster know what's up. It's exactly what I found out and now mine works just fine ;)

http://www.rx7club.com/2nd-generatio...ratch-1048705/

The Bob Skelly link I BELIEVE is the one I was telling you about

Thanks Brian! That is a good explanation for me especially since I will most likely be wiring this from scratch, I'll need something for reference material. After I got off the phone with you I just couldn't go to sleep without inspecting more. Even though we were positive it doesn't contain these wires I checked an extra engine harness (passenger side) that I had laying around and it was loaded with 'T' shaped connectors so I just threw that back in the box. . . I looked for possible remains my OE two pin alternator connector by peeling back the loom on the drive side harness, still nothing. It wasn't there but what I did find was that my alternator was warm (this was after leaving that connection I made on the previous page connected for what, a couple hours?). . Looking into that, I found that I had the 'L' terminal (for dash) connected straight to battery, definitely not right.

http://www.rx7club.com/attachments/3...altinstall.jpg

That link is dead

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.
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.

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.

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.

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

Pin/Terminal. . . whatever, you know what was being referenced. :001_005: 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. .

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.

https://c1.staticflickr.com/3/2794/3...fc3a393a_c.jpg

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

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.

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

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

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

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! :smilielol5:

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.

Gotcha, If you had a switched 12v source connected to the L terminal, chances are it's probably cooked, sorry.

Here's the problem, you're going to have to modify the wiring significantly if you're going to use the chassis wiring (S4) with the S6 alternator and have the idiot light work correctly

Ok, so before you go digging into the harness looking for the mystery wires here's what I would do
Use that existing 12v key wire that you originally had running to the L terminal. Put a small resistor on that wire (I can tell you what I am using tomorrow night) and connect that to the L wire on the S6 Alternator. Yes I realize that this sounds alot like what I just said probably cooked your alt, here's the difference, look at the S6 charging diagram. You'll see the L wire runs to the alt via the ignition switch (so it only sees power when the key is on) through the idiot light in the dash (resistance) and through a diode (one way check valve). So by using that wire on the shock tower (which I'm assuming is B/W or B/Y), you can add a resistor to mimic the resistance of the 1.4W dash bulbs and that solves that problem. Now the S6 will think that your B/W or B/Y wire is being fed through a lamp circuit like it should be.

The S wire on your alt can be temporarily hooked up to the alt charging post or brought back to the battery, either will work fine for testing purposes.

There is a big difference in the way the S4 works from the S5/6. The two main differences are.

The S4 uses the R terminal to turn itself on, and to sense the voltage. The S5/6 uses the L terminal to turn itself on. The S4 doesn't have an S terminal, the S5/6 don't have the R terminal

The S4 uses the L terminal as an output. When the alt goes bad or isn't charging, this terminal latches to ground triggering the idiot light. The S5/6 use this terminal as a turn on. When it sees voltage, it excites the alt.

The S4 doesn't have an S terminal. It uses the R to determine voltage regulation duties. The S5/6 have the S terminal and they use this to sniff the voltage to determine regulation duties.

Does that make sense, at all? Again, this is what I went through 3 years ago

Eh. . What makes the most sense is what I can see drawn out, like the diagram at to beginning of this page lol.

But yes, I see that there's difference in terminals and their requirements, please share your resistor size/part number. . I'm sure it could be beneficial to others as well.

So far things seem pretty clear as to what I need to do. . I just need to get it done. So with what you have said, I'm ditching the idea of searching for the OE wires and will run my leads like mentioned (I believe we're on the same page here).