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RX-7 2nd Gen Specific (1986-92) RX-7 1986-92 Discussion including performance modifications and technical support sections.

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Old 02-23-2017, 09:26 AM   #1
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Default 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?






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Old 02-23-2017, 09:32 AM   #2
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One of the pins on the alternator needs to be connected.

Noob.
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Old 02-23-2017, 09:42 AM   #3
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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?
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Old 02-23-2017, 09:45 AM   #4
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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.
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Old 02-23-2017, 09:45 AM   #5
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I believe switched. The main power wire is of course constant.
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Old 02-23-2017, 09:51 AM   #6
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Sweet. . but what change would it have in my case if that connection is switched 12v?
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Old 02-23-2017, 10:05 AM   #7
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When I connect the bottom pin to the battery lead on the alternator, the whine goes away.
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Old 02-23-2017, 10:06 AM   #8
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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.
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Old 02-23-2017, 10:19 AM   #9
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Could I simply do this, connect here?

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Old 02-23-2017, 10:20 AM   #10
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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
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2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins
1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle
1988 'Vert - In progress
1988 FC Coupe - Gretchen -The attention whore BEAST!


I'm a sick individual, what's wrong with you?
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I think Brian's idea of romance is using lube.
Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion.
You win with your thread. Most everything
It's a truck with a steel gate on the back. Just a statement of fact

Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff....
No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon.
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Old 02-23-2017, 10:20 AM   #11
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I've never had the top wire (the empty spot in the connector) connected to anything. Is that recommended?
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Old 02-23-2017, 10:21 AM   #12
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Quote:
Originally Posted by FC Zach View Post
Could I simply do this, connect here?]
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
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2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter
2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins
1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle
1988 'Vert - In progress
1988 FC Coupe - Gretchen -The attention whore BEAST!


I'm a sick individual, what's wrong with you?
I'm pure Evil
I'm still insane, in the best possible way.
I think Brian's idea of romance is using lube.
Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion.
You win with your thread. Most everything
It's a truck with a steel gate on the back. Just a statement of fact

Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff....
No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon.
-Angry Motherf*cker Mode ENGAGED-
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Old 02-23-2017, 10:22 AM   #13
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Quote:
Originally Posted by FC Zach View Post
I've never had the top wire (the empty spot in the connector) connected to anything. Is that recommended?
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.
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DEALS GAP!! WOOHOOOO!!!!!

2015 Audi S4 - Samantha - Zero Brap S4
2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter
2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins
1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle
1988 'Vert - In progress
1988 FC Coupe - Gretchen -The attention whore BEAST!


I'm a sick individual, what's wrong with you?
I'm pure Evil
I'm still insane, in the best possible way.
I think Brian's idea of romance is using lube.
Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion.
You win with your thread. Most everything
It's a truck with a steel gate on the back. Just a statement of fact

Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff....
No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon.
-Angry Motherf*cker Mode ENGAGED-
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Old 02-23-2017, 10:33 AM   #14
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Ok cool, thanks guys!

One problem though. . I don't remember but does this connector have the "idiot light" wire you speak of?
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Old 02-23-2017, 10:37 AM   #15
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Yes, one wire is straight to the battery, the other pulls through the idiot light.
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DGRR 2009, 2011, 2012 & 2013 - Best FC

DEALS GAP!! WOOHOOOO!!!!!

2015 Audi S4 - Samantha - Zero Brap S4
2004 RX8 - Jocelyn - 196rwhp, 19mpg fuel to noise converter
2000 Jeep Cherokee Sport - Wifey mobile - Now with 2.5" OME lift and 30" BFG AT KO's! So it begins
1998 Jeep Cherokee - 5 spd, 4" lift, 33" BFG's - Rotary Tow Vehicle
1988 'Vert - In progress
1988 FC Coupe - Gretchen -The attention whore BEAST!


I'm a sick individual, what's wrong with you?
I'm pure Evil
I'm still insane, in the best possible way.
I think Brian's idea of romance is using lube.
Your rage caused the meteor strike in Russia. The Antichrist would be proud of his minion.
You win with your thread. Most everything
It's a truck with a steel gate on the back. Just a statement of fact

Motec M820, AIM dash, ported 13B-RE Cosmo, 6-spd trans, 4.3 Torsen, custom twin wg fully divided mani, Custom 4" split into 2x 3" exhaust, Custom HMIC, Custom custom custom custom I like to welder stuff....
No Bolt-ons allowed. Dyno'ed @ Speed1 Tuned by me - 405rwhp on WG.... WM50 cuming soon.
-Angry Motherf*cker Mode ENGAGED-
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