Okay guys and girls, this is going to be a long read. Also, I am going to try to cite sources as I go, because I am NOT trying to pass this off as my own work.

Here goes:

Basically, ever since I went to smaller batteries, I had noticed my car battery was always weak after sitting for a few days. With the Hawker Genesis battery, it was 1-2 days and dead battery. All of you running full size batteries would probably never notice a difference unless the car sat for 2-3 weeks or longer.. Why?

*edit* you will ALSO see unusually high voltages.. I cant explain that one, but the fix corrects it.

source: http://www.nopistons.com/forums/inde...howtopic=41986


Now with my Ammeter, I actually read about .25 Amps, but thats still more draw then should be on the batter in a static state (there will ALWAYS be a slight draw on the battery, but it should be in milliamps NOT amps!).

So whats the deal? From what I have read, the S4 alternator is an "LR" type alternator, and the FD alternator is an "LS" alternator. What the difference is I havent a clue, but from looking at the FD and FC charging circuits I can say this;

The S4 load wire (AKA the "F" or "FIELD") wire 12 Volts is removed when the key is off. On the FD Alternator, that is never removed. So apparently when you retrofit with an FD alternator, when you shut the car off, the FD alt goes into like a max charge mode, which can burn out your regulator.

The Fix:

http://www.rx7.org/public/altxref.html

I made it even simpler. I just cut the field wire and taped the section running back to the car off. Then I soldered a fuse holder to the pigtail coming out of the alternator, and ran it to the B+ post..

Well, it appears to work. I left the battery plugged in overnight, and when I woke up this morning I still had full voltage. I also checked amperage draw on the battery after the mod and its virtually nonexistant. Also, when running, my voltages are solid 14.2-14.4 REGARDLESS of load.

So there it is! Discuss!

 

very good post, prolly worth a archive. hmmm i was hoping this would apply to me too but i guess not.

my battery drains after 4-5 days too but im running a stock alt. Im going to have to fix it after i swap. argh so many problems -.- lol

 

Didn't someone offer the alternator the adapter harness that correctly cut off the B+ wires as a kit, not too long ago?

 

this was covered 1 year ago...

You may wish to use the search function found in the upper right hand corner of the page before posting next time.

 

I thought Icemark plus others had already written what you just wrote and it's in the FAQ? and or the FC3Swhatever website? No doughnut for JRAT either. P.S. a blocking diode on the white/black (series four wiring) would also solve the problem. Not the right fix, but will fix it.

 

Well it didnt come up when I searched.. No need to be rude about it, I am perfectly aware of the location of the search button..

 

does this happen with s5's also or no since the connector is the same

 

i solved the drain problem on my alt like 2 + years ago.

 

The wiring is different however.

The Voltage Referance wire (called feild and load wire above in this thread) is the one that was in question.

See on S4 and S5 models the factory wiring takes it to the key ignition circuit, while the FD wires it to 12 volt battery.

The big problem that this was presenting (and the reason that 90% of the write ups were wrong previous to about a year ago) was that people putting in the FD alt, were revesing the Reference wire and the run wire (the other small gauge wire in the 2 pin alt plug), and while the alt work work, it did not work correctly, and typically burnt out the internal diode on the reference wire.

They were easily reversed, as the wire colors switch around depending on S4 or S5 or S6, and people just were not testing. Instead they just hooked up the wires (usually based off of someone elses wiring mistakes), and suffered from battery draw problems. Of course a multi-meter would show the difference between the two and should be used before and during any electrical work to confirm proper wiring.

Here is the S5 system (S6 simular):

The white/blue wire runs to the ignition circuit on the S5 models, on the S6 models it runs to the battery.
and S4:


These pictures were posted around Mar/04 on teamfc3s and with a FD one I had at the time.

As mentioned above this whole subject was covered more than a year ago in depth both here and on TeamFC3S, as well as covered here in the last week on this board. Its a shame that Rat feels slighted about me mentioning that, and took offense about pointing this out. But I would do the same for anyone.

 

In defense of Mr Rat, who needs no one to defend him in the first place, I'd like to remark that some of those archeived/FAQ items *go round and round and how they turn out nobody knows* (not all humor).

Pay no heed to me, I'm the fellow who didn't know what the Motor Fail Box did in life.

 

Well, its a shame that the mods feel it necessary to treat the older members of this board like newbies by telling them to search...

 

there is also another issue with switching to FD alternators. Check out this link.

http://www.teamfc3s.org/forum/showth...threadid=44532

 

wow, i never knew this!! maybe the write will help ay least 1 person!! me!!! thanks j-rat.. though i can honestly say i never had any draining problems.(s4 alternator) my battery did mysteriously just died one day on the way to work.

 

Ok, since I have no knowledge of how the charging system works on s5's, what do I need to do when I get an FD alternator to put on my s5? Please work with us since it seems there are many people who are confused by this. Have it stickied or put in the archive if needed.

 

Alright, after reading through the post again, this is what I understand. The field wire brings a +12v to the alternator, when this voltages changes (drops I presume) the alternator will attempt to charge the battery. The problem is, on an FD, the wire is always carring this +12v while on FCs, the wire drops to +0v when the ignition is not on. So in turn, the FD alt sees +0v and attempts the charge the battery, which actually is a negative effect hence draining the battery. So it seems, a simple fix would to be to cut this wire, fuse it, and run it into another part of the alt that always sees +12v regardless of which model car it is on.



Please either confirm or deny what I have typed and tell me what is possibly wrong with my statement. Thank you.

 

yep, that will work when using a FD alt, on a S4 or S5.

The big key is just to make sure not to get the reference and run wires mixed up.

 

Thanks Icemark, I appreciate it.

 

If more threads like this one and others, that are very helpful, were added to the archive where they could be easily found than there wouldn't be as big of a problem with finding stuff. For some reason stuff like this doesn't get archived like it shoud be.

 

people are trying to get rid of this by bypassing this chargeing thing the alt does when the cars off.. is there any benifit to get it working right. maybe running a wire from teh battery to the alt where it wants to see the 12V?