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How to hook up "voltage sensing wire"

2K views 16 replies 5 participants last post by  EOD Guy 
#1 ·
'66 Nova,new AAW stock replacement wiring, Int. reg. alt. I've read the MAD Enterprise article, but it doesn't state which wire from the alt is the one that senses voltage. Is it one of the wires from the 2-wire connector? If so, does that wire go to the horn relay? I want to make sure that I have the remote voltage sensing.Thanks.
 
#2 ·
The "2 wire plug" has two terminals........

An external reg is wired follows:

F terminal goes to the #1 terminal on the alt
1 terminal goes to the #2 terminal on the alt
2 terminal goes to the hot side of the electrical system and is normally spliced into the main feed/large lug on the alt (use 5-6 feet of new 10g wire before you splice in, I explained it below)
3 terminal goes to the idiot light or if you don’t have an idiot light a switched 12v source (I explain below)


Since you are modernizing, I would go with an internal regulator....... far easier to wire and maintain.

On the alt (internal regulator) there are basically 3 connections

The Alt pig tail has terminals 1 and 2

Terminal #1 from the alt goes to the one side of the idiot light on the dash. The other side of the idiot light goes to a switched 12v source (hot when the key is in the run position) This is the exciter wire and tells the alt to start producing juice. The idiot light does not get a ground wire, it gets a ground from the internal regulator in the alt when the alt isn't spinning. That's why it lights when the key is turned to run but the engine isn't running, and it goes out when the engine starts. You do not have to have an idiot light or a resistor, you can have just a switched 12V running to the #1 terminal and it’ll work just fine.

Terminal #2 from the alt goes to the hot side of the wiring system, normally it’s spliced into the hot feed leading to the fuse box. This is the sense wire, it tells the alt to produce more or less juice depending on the demands of your electrical system.

The large lug on the back of the alt is the output wire or charge wire and is normally tied directly to the pos post on the battery via a large gage battery cable.

On some installations the alt may need a ground cable, (I never use one etc….)
 
#3 ·
Yes, the voltage sensing wire goes to the threaded stud on the horn relay. Basically, you want to sense the voltage at a location that accounts for the worst of the voltage drops. Resistance in the wiring and connections will drop voltage, which leads to the GM hot starter problem (among other problems). The sense wire allows the regulator to compensate for this and bump the output voltage up slightly. If you wanted to, you could even put that sense wire in another location if you felt there was a worse voltage drop, but the factory put it at the horn relay.
 
#5 ·
Umm, guys...
'66 Nova,new AAW stock replacement wiring, Int. reg. alt. I've read the MAD Enterprise article, but it doesn't state which wire from the alt is the one that senses voltage. Is it one of the wires from the 2-wire connector? If so, does that wire go to the horn relay? I want to make sure that I have the remote voltage sensing.Thanks.
He already has an internal regulated alternator.... :)
 
#6 · (Edited)
I explained the External regulator connections, because of the new harness comment and the mention of the horn relay and then went on to explain the Internal connections. I assumed he was up grading to the new Alt/harness and couldn't make sense of the older components and the new harness connections etc...... But thanks for pointing it out.
 
#7 ·
what I wanted to find out,was , did i still need a voltage sensing wire setup, as explained in Mad Enterprise's article. Either it's too technical for me or it didn't mention that if you have an int. reg alt that you don't need to do this. I do wanna have a good electrical setup. Thanks to all who responded.:thumbup:
 
#9 ·
IMO...... all alts have a voltage sensing wire/circuit. On a one wire it's a shunt internal to the alt. IMO it's not the ideal setup because it requires the alt to spin up enough to place a demand on the circuit in order for it to start producing juice etc........ The three wire requires the same principal but at a much lower rpm. That's not exactly how it works but close enough.......

Adding approx 6 feet of wire between the #2 terminal and the splice point, adds resistance and acts as a buffer (sort of) and give the circuit a more accurate sense of the demands on the electrical system. This buffer prevents the circuit from mass fluctuations or "ON"" "Off" "On" etc......
 
#11 ·
Adding approx 6 feet of wire between the #2 terminal and the splice point, adds resistance and acts as a buffer (sort of) and give the circuit a more accurate sense of the demands on the electrical system. This buffer prevents the circuit from mass fluctuations or "ON"" "Off" "On" etc......
I have about 1.5' space from Bat to junction. Should I use a smaller Gauge wire to simulate the resistance from a 6' wire? If so, what size?
 
#15 ·
Take a pic of the back of your alternator and post it up. If you have a true "one wire" alternator you will not be able to add the sense wire. You will have to get a 3 wire alternator. If you have a three wire alt it will have the 2 pin connector with the sense and light wires.
Mark
 
#17 ·
Soooooooo, If you have a 2 wire plug and two wires coming out of it, and both of them go into the wiring harness of the car........ you probably have a three wire alt.

If you have a 2 wire plug and two wires coming out of it, and the #2 terminal is going to the output lug (on the rear of the alt) you still have a three wire alt.......... it's just has the #2 wire or sense wire wired to the output lug. It's wired like a one wire, it'll work but not the way I'd do it.
 
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