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  • Alternator help!! (94 Prostar 205)

    Boat: 1994 Prostar 205
    Motor: GM Indmar 5.7L

    Hey guys, need a little help with my alternator. Had this one rebuilt 2 years ago and not it seems it’s not charging anymore.

    It only has two wires that connect to the back

    Red wire - power
    Purple wire - ????

    Does anyone have and tricks to test if the alternator has gone bad again? (Seems weird since it was rebuilt 2 years ago)

    What terminal should the purple wire be connected too?

    Do you recommend any replacement alternators? Looking to add a second battery to run my audio.

    Thanks.

    - Chris




    Sent from my iPhone using Tapatalk

  • #2
    The purple wire is the "exciter" wire. It gets voltage from the key switch "on" circuit and tells the alternator when to do its thing. Where did you have the alternator rebuilt? They will be able to bench test it for you. Most decent auto parts stores will be able to as well.
    '96 ProStar 205 SD LT-1

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    • #3
      Where does the purple/exciter wire connect?

      There are two terminals where it can connect at the bottom...wondering if I have it connected to the wrong terminal.

      It was rebuilt at a local shop here in Dallas that is conveniently now out of business.

      I took it to autozone and they said they didn’t have the “right connections” to test. Going to take it somewhere else tonight. I will also take good pictures while I have it off tonight to see which terminal I have the purple wire connected.


      Sent from my iPhone using Tapatalk

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      • #4
        Originally posted by chrismi25 View Post
        Where does the purple/exciter wire connect?

        There are two terminals where it can connect at the bottom...wondering if I have it connected to the wrong terminal.

        It was rebuilt at a local shop here in Dallas that is conveniently now out of business.

        I took it to autozone and they said they didn’t have the “right connections” to test. Going to take it somewhere else tonight. I will also take good pictures while I have it off tonight to see which terminal I have the purple wire connected.
        AutoZone didn't have the "right connections?" Didn't have the right employees is more honest. The right connections for that alternator are two alligator clips.

        If one of your terminals is labeled EXC, I think that is the terminal you need.
        '96 ProStar 205 SD LT-1

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        • #5
          Regarding trick to testing... what does voltmeter say when motor starts?

          Regarding rebuild did rebuilder keep CGA parts on it?

          Sent from my SM-G955U using Tapatalk
          sigpic...A bad day water skiing still beats a good day at work...1995 Pro Star 205....

          Comment


          • #6
            Mike - I'm not sure if they used CGA parts or not. I've had problems with this alternator for years so I just went ahead a pulled the trigger and bought a new one this morning. Went with:

            Delco Marine 105Amp - https://www.dbelectrical.com/product...e-adr0334.html

            Plan on doing a dual battery setup. Going to get all new wires for both batteries. What size wires do you recommend?

            http://www.genuinedealz.com/marine-wire

            Comment


            • #7
              Originally posted by chrismi25 View Post
              Mike - I'm not sure if they used CGA parts or not. I've had problems with this alternator for years so I just went ahead a pulled the trigger and bought a new one this morning. Went with:

              Delco Marine 105Amp - https://www.dbelectrical.com/product...e-adr0334.html

              Plan on doing a dual battery setup. Going to get all new wires for both batteries. What size wires do you recommend?

              http://www.genuinedealz.com/marine-wire
              That one is a one wire setup, meaning ground is through block, and no exciter wire. It should work but will requiremsome,wiring mods. As to wire gauge, check a chart based on amperage and distance to determine min wire gauge. For example 10ft @ 120 amps needs 2awg size minimum. Many just overdo it and use 0awg wire size.

              Comment


              • #8
                Originally posted by chrismi25 View Post
                Mike - I'm not sure if they used CGA parts or not. I've had problems with this alternator for years so I just went ahead a pulled the trigger and bought a new one this morning. Went with:

                Delco Marine 105Amp - https://www.dbelectrical.com/product...e-adr0334.html

                Plan on doing a dual battery setup. Going to get all new wires for both batteries. What size wires do you recommend?

                http://www.genuinedealz.com/marine-wire
                That one is a one wire setup, meaning ground is through block, and no exciter wire. It should work but will requiremsome,wiring mods. As to wire gauge, check a chart based on amperage and distance to determine min wire gauge. Most just overdo it and use

                Comment


                • #9
                  Originally posted by chrismi25 View Post
                  Mike - I'm not sure if they used CGA parts or not. I've had problems with this alternator for years so I just went ahead a pulled the trigger and bought a new one this morning. Went with:

                  Delco Marine 105Amp - https://www.dbelectrical.com/product...e-adr0334.html

                  Plan on doing a dual battery setup. Going to get all new wires for both batteries. What size wires do you recommend?

                  http://www.genuinedealz.com/marine-wire
                  That one is a one wire setup, meaning ground is through block, and no exciter wire. It should work but will require some wiring mods. As to wire gauge, check a chart based on amperage and distance to determine min wire gauge. For example 120amps a 10ft requires 2awg minimum. Many just overdo it and use 0 gauge.

                  Comment


                  • #10
                    Originally posted by Rossterman View Post
                    That one is a one wire setup, meaning ground is through block, and no exciter wire. It should work but will requiremsome,wiring mods. As to wire gauge, check a chart based on amperage and distance to determine min wire gauge. For example 10ft @ 120 amps needs 2awg size minimum. Many just overdo it and use 0awg wire size.

                    Rossterman - When you say “require some wiring mods” does this just mean higher gage wires based on the distance?

                    Or is there other wiring mods I will have to make for this to work correctly?

                    Last question: The wire gauge going from the battery to starter is 2awg. The wire gauge going from the alternator to black box is smaller, maybe 10awg. Should I increase the size of this wire if I increase the size of the starter wire to 0awg?

                    Thank you in advance for all the help guys. I’m not the best when it comes to electrical.

                    Beers[emoji482] on me if you guys are ever in the Dallas area!


                    Sent from my iPhone using Tapatalk

                    Comment


                    • #11
                      You will need to disonnect and keep the purple wire from touching ground as it will be carrying 12vts when key is on. As to red power wire, IIRC my original set up went to the positive post on the starter which was where the positive cable from the battery was landed as well. The starter to battery cable was already 0/1 gauge but the alternator to starter was much smaller. I ran similar (0/2 awg IIRC) from the alternator to the starter post to handle the extra current the higher output alternator provided. I didn’t need to change the starter to battery run as it met the requirements based on total length (distance from atl to starter + dist from starter to battery)

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                      • #12
                        That makes sense.

                        Thank you for this insight. Very much appreciated.


                        Sent from my iPhone using Tapatalk

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                        • #13
                          Please keep us posted how your single wire alternator install goes. My 94 205 has the same alternator and I am looking for cheaper replacement solution like the one you found. Is there any real advantage to keeping the stock 2-wire setup?
                          1983 Stars & Stripes
                          1994 Prostar 205 (5.7 TBI)

                          Comment


                          • #14
                            Originally posted by MC351stars View Post
                            Is there any real advantage to keeping the stock 2-wire setup?

                            Yes/No - in application if you are making "enough" juice with the alternator you'll not run out.

                            A single wire alternator is basically a fixed voltage power source to the system that tries to maintain a constant 14.whatever output to the battery. High amp single wire alternators can just keep upping the output if the feed side is low (like if you turn on your ballast pumps and the radio and a fan or whatever else you use on your boat).

                            This is a condition that can be remedied by systems that have a remote sensing wire that is looking at the voltage between the battery and the system instead of just the output voltage of the alternator.

                            Is it a big problem? Not if you aren't draining the battery too much, if you are then having a remote sensing alternator is a big plus because the system will increase voltage to help boost up the battery faster. Also do consider a single wire as a "single wire + ground and add an ancillary ground wire from the alternator to the block bypassing the mount. On my buddy's boat if you took a jumper from the case of the alternator to the engine ground the system voltage went up .2 volts.

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