Sense wire for 12si alternator - Page 2 -
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Unread 06-11-2012, 07:38 PM   #16
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1997 TJ Wrangler 
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...I might add that I'm familiar with, and talking about, the wiring on my '78 CJ5. Newers systems (computerized) - that could possibly be the case - i'm just not familiar with that setup perhaps.

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Unread 06-13-2012, 09:43 PM   #17
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Ok - so the debate stands - battery connection, coil connection, or fuse box/horn relay connection? (Back to the alternator is out, that is what I am trying to avoid.) Does anyone know if there is a 12si spec sheet or something, which shows what the manufacturer thought?
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Unread 06-14-2012, 06:43 AM   #18
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Ok of the 3 options presented, all "work" which is why you have read them, but some work better than others, and with some draw backs.

1. Loop to + battery terminal. This connection is the most "Battery" friendly as it ensures that the battery always receives proper voltage regardless of whatever else the electrical system is doing.

2. Loop to Coil. Coil once started runs through a resistor which drops the voltage down. this makes the sense wire see low voltage and tells the alternator "i need more voltage" the alternator says "OK" and runs up until it hits the internal failsafe around 15v.

3. Loop to fuse block. This one is kind of inbetween 1 and 2. The entire jeep in stock config is ran of a single 10ga wire. When running headlights, heater on full you have significant voltage drop. (Mine goes down to 12.3 in that configuration) If I hooked up my sense wire to the fuse block. The sense wire would say "I need more voltage" and hit the internal regulator and stop around 15 volts output, where the fuse block would be receivning less than that because of the volt drop. This is a good option if you want brigher headlights. If you live in suburbia like me bright headlights are not a big deal.

4. Short wire looping to + output is about the same as hooking to the battery as there is very little voltage drop if you have a large wire outputting from the alternator under normal curcumstances. Its slightly easier to hookup and I dont think there is any benfit of doing the battery hookup personally. I mine is wired in this configuration.

The battery is pretty ok with getting 15v for a while Mine ran for 6 months w/oo issue like that when my sense wire connection got disconnected and stopped working.
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Unread 06-14-2012, 07:17 AM   #19
John Strenk
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1976 CJ5 
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I may be mistaken on the Coil connection. That might be the field connection to turn the field off and on. Not the voltage sensing wire.

The short wire looping is the way mine is done also.

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Unread 06-14-2012, 10:16 AM   #20
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John, or anybody really, which would you suggest for a 10si and HEI? I've got a blank slate (roller and Painless kit). BTW painless just = less pain. less pain than what, I don't know.
The only "FINISHED CJ" is the stripped one in a junkyard w/a bent frame.
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Unread 06-14-2012, 11:47 AM   #21
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Sherlock --- your comment summed it up perfectly. From what I've read on other "non-jeep" related forums and other discussions boards specific to talking about alternator/charging systems, your option #3 setup is suggested to be the "purposed" way the sense wire input is used. All the sense wire does is basically "monitor" the electrical system at whatever point you connect it to... when voltage drops at the monitored point (typically due to higher current draw which can not be fully accommodated because of resistance in the wire, connections, etc) then the alternator says "hey-the system needs more from me" and pumps up to a little higher pressure / VOLTAGE to overcome the resistance.
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Unread 06-15-2012, 06:46 PM   #22
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This afternoon I popped the hood to do a visual when my mother in law came home with the jeep and the looped sense Wire off the charge output looked odd. I touched it and sparks flew.

Good thing I had a bag of those connectors.
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alternator , wiring alternator plug
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