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post #1 of (permalink) Old 09-22-2006, 05:48 PM Thread Starter
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Alternator hookup

I need to know were to hook up a wire on my alternator.



The wire from the BATT terminal on the back of the alternator goes to my guage and then to my dual battery isolator. The B terminal goes to the wire harness and into the fuse box I think. The wire on Terminal A is the one with the the ring terminal that is just hanging there. That is the one that I am not sure how to hook up.
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post #2 of (permalink) Old 09-22-2006, 05:57 PM
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Re: Alternator hookup

Hmm, my '85 doesn't have one! BTW get RID OF the electrical tape, that is just frustration waiting to happen! It's good for a quick fix, but solder/shrink wrap is the only way to reliability!

And for ease of use I use solder weld, better than a 3rd hand when soldering connections:

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post #3 of (permalink) Old 09-22-2006, 05:58 PM
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Re: Alternator hookup

That goes under the output lug. It sends the output voltage around to the regulator, so that the regulator knows what the voltage is and can adjust it accordingly. It's commonly called the 'sense' wire.
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post #4 of (permalink) Old 09-22-2006, 08:15 PM Thread Starter
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Re: Alternator hookup

[ QUOTE ]
That goes under the output lug. It sends the output voltage around to the regulator, so that the regulator knows what the voltage is and can adjust it accordingly. It's commonly called the 'sense' wire.

[/ QUOTE ]

I hooked it up like that and it does not work. I get nothing on the guage and when I put a meter on the BATT terminal I get .8 volts. I took the alternator in to Checker and it tested OK. There must be something wrong with the wire to the B terminal. Anyone have any suggestions?
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post #5 of (permalink) Old 09-22-2006, 10:07 PM
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Re: Alternator hookup

That wire is set up to do a bootstrap.

Two things are wrong - there should be voltage on the big output terminal at all times. You said it goes to the gauge - an ammeter? Where's he other side of the ammeter go? Should be to the battery.

That smaller red wire - the "sense" line - should go to the battery + through a separate wire. It can be connected to the back of the alternator to the big outpu terminal, but then it's not going to properly charge the battery. It'll give the battery a lower charge than it should have.
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post #6 of (permalink) Old 09-22-2006, 10:36 PM Thread Starter
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Re: Alternator hookup

[ QUOTE ]
there should be voltage on the big output terminal at all times. You said it goes to the gauge - an ammeter? Where's he other side of the ammeter go? Should be to the battery.

[/ QUOTE ]

Yes, an ammeter. The other side goes to a battery isolator that charges two batteries.

[ QUOTE ]
That smaller red wire - the "sense" line - should go to the battery + through a separate wire. It can be connected to the back of the alternator to the big outpu terminal, but then it's not going to properly charge the battery. It'll give the battery a lower charge than it should have.

[/ QUOTE ]

Should I run the wire with the ring termainal directly to the battery instead of the BATT terminal on the alternator?
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post #7 of (permalink) Old 09-23-2006, 08:15 AM
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Re: Alternator hookup

The small white wire needs to have 12 volts applied to it when the engine is running. But you don't want it hot all the time because it will slowly drain the battery. That provides a little field current which the alternator needs to bootstrap itself up. Without that the alternator might wake up if you spin it really fast, or it might not.

The small red wire is the sense line. It tells the regulator what the voltage is so that the regulator can adjust the alternator output accordingly. If you hook it to the alternator output lug the regulator will regulate the voltage at the output lug.

If you do as RRich suggests and run that wire to the battery, the regulator will regulate the voltage at the battery.

Rich and I disagree on the significance of that. I say that the difference is too small to worry about if the vehicle doesn't use a lot of electricity, and have taken measurements on my (minimalist) Jeep that support that standpoint.

Rich says that the difference is significant, and I agree with him if it's a vehicle with a big constant electrical load, like an OTR truck or an ambulance.

But it's easy to run that sense line somewhere closer to the load, and it absolutely won't hurt anything. You can put it in the loom right along with the big output wire, run it to the solenoid and put it under the same terminal.
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post #8 of (permalink) Old 09-23-2006, 06:18 PM Thread Starter
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Re: Alternator hookup

I traced the white wire back to a 12v switched source at by the fuse box. The wire was broken so I ran a new wire and everything seems to work great.
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post #9 of (permalink) Old 09-23-2006, 06:24 PM
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Re: Alternator hookup

Great! Where was the break?
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post #10 of (permalink) Old 09-23-2006, 07:09 PM Thread Starter
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Re: Alternator hookup

Right before it went into to firewall.
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