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SIII Alternator wiring order on back of alternator

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  • SIII Alternator wiring order on back of alternator

    I noticed that the wiring connector on the back of my SIII's alternator was busted and half missing so I figured I would get a new plug and clean up the terminals if needed. On pulling off the connector (Lucas type I think, 3 wires in a row - 1 small and 2 larger terminals), I was wondering if it mattered the order of the two larger terminal wires? I ask because of the two supposed brown wires (one of mine looks to be a replacement 16 gauge red wire the other a 10 gauge brown) the red wire was in the middle and the larger brown on the outside which is opposite of what I see on the replacement connectors online.

    I know both the wires lead back to the same lug on the starter relay, and one wire I guess is for charging and the other sensing into the alternator, but is their order important because I think mine are wrong. I haven't had any charging/electrical issues that I can detect.

  • #2
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    • #3
      Alright I'll take that as it doesn't matter which way the alternator wires go. Thanks


      • #4
        The sense and charge wires may connect to the same location on the starter relay, but the charge wire is typically a heavier gauge wire as it carries the alternator output to the vehicle loads, while the sense wire is a much smaller wire with a voltage input to the regulator in the alternator. It isn't carrying any load, unlike the charge wire. If you get them reversed, you could fry the smaller wire....



        • #5
          I guess I am back to square one with my question


          • #6
            The connections are different sizes. You can’t plug the sense wire onto a charge terminal as they are physically larger. The two larger charge wires end up connected so the position doesn’t matter.


            • #7
              Well I did a little more google research and found the following, which I won't take as gospel but it sounds good.

              It states that the there were a couple of ways how the spades were used on the ACR16 3pin Lucas alternators: one where both the alternator's brown wires were connected within the rectifier so both wires were "output" - machine sensing or really a two-wire alternator, and one where the wires were isolated from one another so one was "output" and the other "sense" - battery sensing or true three-wire alternator.

              It also states that for the higher amp ACR18 alternators they were the machine sensing or two-wire type with two larger brown wires from the solenoid to the alternator. I believe the ACR18 was what was fitted standard to the 71-74 North American SIIIs. When I was originally mentioning that my alternator wiring consisted of a 10 gauge brown, 16 gauge brown/yellow and a 16 gauge replacement red wire I didn't mention that the red wire was actually attached at the alternator by a small bit of 10 gauge wire so mine was probably two 10-gauge wires which goes along with what the other link says for ACR18s.

              I haven't looked inside my replacement alternator to see if the two larger terminals are connected or not but either way I think while replacing the plug I'm going to just run another large wire replacing the replacement red wire and call it a day.