Alternator question, battery is discharging quickly.

FC Zach · 02-23-2017, 09:26 AM

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?

djmtsu · 02-23-2017, 09:32 AM

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

Noob.

FC Zach · 02-23-2017, 09:42 AM

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?

FC Zach · 02-23-2017, 09:45 AM

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.

djmtsu · 02-23-2017, 09:45 AM

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

FC Zach · 02-23-2017, 09:51 AM

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

FC Zach · 02-23-2017, 10:05 AM

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

***TitaniumTT*** · 02-23-2017, 10:06 AM

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.

FC Zach · 02-23-2017, 10:19 AM

Could I simply do this, connect here?

***TitaniumTT*** · 02-23-2017, 10:20 AM

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

FC Zach · 02-23-2017, 10:20 AM

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

***TitaniumTT*** · 02-23-2017, 10:21 AM

Quote:

Originally Posted by FC Zach

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

***TitaniumTT*** · 02-23-2017, 10:22 AM

Quote:

Originally Posted by FC Zach

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.

FC Zach · 02-23-2017, 10:33 AM

Ok cool, thanks guys!

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

***TitaniumTT*** · 02-23-2017, 10:37 AM

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

02-23-2017, 09:26 AM	#1
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	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? __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-23-2017, 09:32 AM	#2
djmtsu My minds tellin' me no... Join Date: Feb 2008 Location: Murfreesboro, TN Posts: 4,043 Rep Power: 22	One of the pins on the alternator needs to be connected. Noob. __________________ 1976 Mazda Cosmo RX-5 1976 Mazda Cosmo RX-5 2003 Toyota Tundra TRD 2015 Toyota 4Runner SR5

02-23-2017, 09:42 AM	#3
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	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? __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-23-2017, 09:45 AM	#4
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	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. __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-23-2017, 09:45 AM	#5
djmtsu My minds tellin' me no... Join Date: Feb 2008 Location: Murfreesboro, TN Posts: 4,043 Rep Power: 22	I believe switched. The main power wire is of course constant. __________________ 1976 Mazda Cosmo RX-5 1976 Mazda Cosmo RX-5 2003 Toyota Tundra TRD 2015 Toyota 4Runner SR5

02-23-2017, 09:51 AM	#6
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	Sweet. . but what change would it have in my case if that connection is switched 12v? __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4 Last edited by FC Zach; 02-23-2017 at 12:01 PM.

02-23-2017, 10:05 AM	#7
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	When I connect the bottom pin to the battery lead on the alternator, the whine goes away. __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-23-2017, 10:06 AM	#8
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	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. __________________ -The Angry Stig- 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 Motherfcker Mode ENGAGED-**

02-23-2017, 10:19 AM	#9
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	Could I simply do this, connect here? __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-23-2017, 10:20 AM	#10
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	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 __________________ -The Angry Stig- 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 Motherfcker Mode ENGAGED-**

02-23-2017, 10:33 AM	#14
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	Ok cool, thanks guys! One problem though. . I don't remember but does this connector have the "idiot light" wire you speak of? __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-23-2017, 10:37 AM	#15
*TitaniumTT* Test Whore - Admin Join Date: Mar 2008 Location: Right Behind you son Posts: 4,581 Rep Power: 10	Yes, one wire is straight to the battery, the other pulls through the idiot light. __________________ -The Angry Stig- 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 Motherfcker Mode ENGAGED-**