Rotary Car Club - Alternator question, battery is discharging quickly.

Rotary Car Club (https://rotarycarclub.com/index.php)

- RX-7 2nd Gen Specific (1986-92) (https://rotarycarclub.com/forumdisplay.php?f=37)

- - Alternator question, battery is discharging quickly. (https://rotarycarclub.com/showthread.php?t=19156)

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.

Quote:

Originally Posted by FC Zach (Post 339872)

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?

Quote:

Originally Posted by djmtsu (Post 339873)

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....

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.

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/

Quote:

Originally Posted by RockLobster

I wired my race car (s5 alt) without any of the stock harness, getting the alternator to work properly was the biggest pain. Until I basically learned what all the wires do. You need all 3 wires connected. If you are not using the stock harness you need to create these circuits or the alternator will either not work or kill itself.

B terminal is the obvious part. That's the charge wire. It...um...charges the battery...min 4 gauge IMO.

S terminal needs direct battery signal, can't go through a relay or any switch. It can go through a fuse. This is the "sense" wire. It tells the internal alternator voltage regulator what the battery voltage is and thus how much "charge" to put into the system. The closer you connect this to the battery the better your alternator will work. If you just jumper it to the charge post it really wont fluctuate voltage output to adapt to battery state and load conditions.

And last but not least the one that had me thinking like you. The L terminal which is where the excite wire connects. Yes it does power the idiot light. It does this because current flows if there is a substantial difference between the system or batt voltage and the alternator charge voltage. This terminal/wire must be connected because it is in effect what "turns on" the alternator. BUT and this is a big but. YOU CANNOT JUST CONNECT IT TO A HOT WIRE OR THE BATTERY. It must have resistance or you will destroy the alternator voltage regulator and the alternator will need to be rebuilt because it will not regulate voltage, the voltage will just rise with RPM up to 16-17 volts. I don't have to tell you that is bad. SO, the factory dash has two parallel sources of internal resistance. One is a light, the other is a standard resistor. You CAN NOT skip the resistor because if you just use a light and the bulb burns out, guess what, your alternator shuts off. So, you have to wire this terminal back to +12v (again no relays upstream for this one too) but you must also put a roughly 120-150 ohm resistor on this wire. Up to you if you want a charge light in parallel. It appears in some cases (3rd gen rx-7 and other cars) the factory dashes just use multiple idiot lights as the redundant sources of resistance for this. So if one bulb burns out the alternator does not just quit working. If you do put a charge light in parallel you need to put a diode in also or the light will be on all the time. The diode should only allow current flow TO the alternator. It needs to BLOCK current flow back from the L terminal.

I think in your case your alternator may be damaged or isnt charging because it isnt turned on. But your assumption that the alternator "stays on" when the engine is not running is incorrect. This isn't actually possible. Without the little wheel spinning on the front of the alt it's basically a paper weight, it cant be on without being driven. But, if you damaged the voltage regulator it may create a bleed. If i recall correctly when i blew one trying different things to get it to work properly (read just put unresisted +12v to the excite terminal) it self excited after that and would not regulate voltage at all.

Some reading for you: http://bob_skelly.home.comcast.net/~...ternator1.html

This basically explains all this, probably more eloquently than i did.

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