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How to make a charge light wire with an LS smart alternator

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    How to make a charge light wire with an LS smart alternator

    So I have the L98 in my FD complete with the VE commo fancy 2 wire alternator. Runs fine but I have no charge light. The FD had a traditional alternator that was grounded presumably when it was outside it's happy range of 13.5-14.8V or whatever, and showed +ve voltage when it was ok. Diagrams below.

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    Now I need to replicate this because my ABS isn't happy and I want a charge light. I'm too dumb to figure it out. I'm thinking either a relay with the E38 ECU sending a "She's all good bro" light if one exists through HP tuners, or some fancy electro-pixie gizmo that does it for me. Anyone got the clues?
    Attached Files

    #2
    I know nothing about what you can fuck with on the ECU but surely voltage > x => output low and vice versa would be about the simplest mod possible so if you can do anything mod wise that would be it.

    Otherwise it would be some what simple to come up with a standalone circuit to do the same (if it doesn't already exist).

    Note that voltage is not exactly how alternator lights work but would somewhat achieve the desired effect if you set a changeover point high enough i.e. it would need to be about 13V otherwise any voltage measurement device (ECU or anything else) would not be able to see the difference between the battery and the alternator.
    Last edited by Shonky; 29-01-20, 05:41 PM.

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      #3
      I spoke to someone who knows the HP tuners software and it looks like the ECU can’t do it.

      I found this which could do the trick? https://bluewireautomotive.com/produ...-signal-module

      but keen to know what you mean about the regulator function. I don’t understand the diagram but looking at where it is in the system i think it has to show ground when it’s not 12-14V so the light illuminates.

      Comment


        #4
        That link is for those 1 wire charge wire alternators.

        Loom for alternator/starter is completely seperate to ecu etc

        Can you find original charge light wire in engine bay by tracing factory loom to hook it up to alternator wire?

        ABS light flickers on?.
        an easy fix is get a mate to drive in front of you at 60 then 80 then 100 and mark in on your speedo with some liquid paper.

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          #5
          The E38 ECU runs two wires to the alternator with fancy PWM or some pixie science shit as per factory. I believe the commodore BCM plays a role too and perhaps my alternator defaults to 13.8V or something but it works fine as it is. I just don’t have a charge wire.

          if I connect the wire highlighted above (RX7 OEM charge light and ABS wire) to ignition the charge light won’t illuminate if it’s under or over charging I don’t think. It really needs to pull to ground if it’s below 12V I think? Hence why I thought I could use that link above

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            #6
            You can always use an ls1 alternator and wire it up normal like

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              #7
              Yeah I know but it's just so deep in there!

              In all seriousness it is a fallback option but it works fine just nice to have a charge light

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                #8
                In the E38 pcm the Alt light is controlled by the BCM ( Via serial data ,Assuming that you have not used a BCM so it`s not a option ) my suggestion is to use a Ls1 alternator to get a no charge Light . Also by tapping into the Aternator light circuit , you can use that circuit to switch the ABS on. There`s a input on the passenger side of the FD engine bay for the ABS activation. I can take a pic next time I go make a coffee? Falling the alternator change I would just install a switch in the cabin to activate the ABS when required. HTH
                Originally posted by bigmuz
                Really who cares- you go to the pub and come home with no money smashed. The price of beer is kinda irrelevant.
                Originally posted by JZK25
                I bet it thong slaps like a boss with that exhaust on it. 253 yo!

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                  #9
                  Thanks Paul appreciate the input. I'm just about finished tracing all the wiring from the ABS unit so hopefully I can rig up something to check it works and then implement a fix. Any photos or info you have would be appreciated

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                    #10
                    Shit assumed was similar to earlier ls shit.

                    What would next option be...a resistor?
                    an easy fix is get a mate to drive in front of you at 60 then 80 then 100 and mark in on your speedo with some liquid paper.

                    Comment


                      #11



                      Click image for larger version

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ID:	7109327 No problem , The ABS activate wire is the green one with the red bands on the top right of the small plug.
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                      Attached Files
                      Originally posted by bigmuz
                      Really who cares- you go to the pub and come home with no money smashed. The price of beer is kinda irrelevant.
                      Originally posted by JZK25
                      I bet it thong slaps like a boss with that exhaust on it. 253 yo!

                      Comment

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