Off season electrical re-wire

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  • Indy
    Senior Member
    • Oct 2014
    • 41

    Off season electrical re-wire

    I have a late model A4 and have decided it's time to overhaul the electric. Most of the wiring from the engine appears to be original, all of which leads to a terminal block. The block is suspended above the engine, hanging from what appears to be at least 10 feet of wires - all correct color coding and neatly wrapped in a loop that is tacked to the engine compartment ceiling. That loop of excess wires terminates in a trailer type plug that leads to the gauge panel. It's quite a mess and seems like a very likely, eventual point of failure that will be difficult to diagnose if there is a problem.

    I plan to do the following and would appreciate words of advice. There is nothing complicated about this, but I'm just somewhat experienced in re-wiring systems on this boat.

    1) Remove the trailer plug and permanently mount the terminal block to the engine compartment wall. I've added a couple photos, one of the terminal block, the other of the plug. I don't have a good picture of the wire loop, but it appears to be pristine wire, almost still looped the way it was whenever it was installed.

    2) Use the existing excess wire that is tacked to the ceiling to wire from engine components to the block.

    3) Use existing excess wire to complete connections directly from the terminal block to the gauges.

    4) Replace all the gauges and potentially the ignition & fan switches.

    5) Clean all connections.
    Attached Files
  • Dave Neptune
    Afourian MVP, Professor Emeritus
    • Jan 2007
    • 5115

    #2
    Great idea!! The "trailer plug" is the subject of many electrical trouble shooting threads and problems on this site. Another is to get away from the ammeter and go to a volt meter in the cockpit as the back and forth runs just costs power. If you still want an ammeter get one that uses a shunt so it can be mounted close to the output and the gage can be mounted anywhere you wish. I also suggest if you are going to use the existing wire that you shorten as much as you can and replace any of the wire that shows "black wire" corrosion.

    Do mount the connection block somewhere solid and coat the block and wires with dielectric silicone or equivalent to seal them from moisture.

    Sticking with the color coding of the stock engine is nice for trouble shooting but not absolutely necessary especially if you make a drawing or tag the wires as to what they are.

    Dave Neptune

    Comment

    • ndutton
      Afourian MVP
      • May 2009
      • 9780

      #3
      Here is my Cliff Notes version of general considerations posted 10 years ago:

      https://www.moyermarineforum.com/for...5&postcount=16 and repeated here

      (In direct response to another member's question on grounds)Technically you can have as many ground wires on the engine as you want. I'm trying to nudge you in a direction with the (ground) bus bar of a professional looking and superior installation. Train the wires neat, clean and parallel, support the wires independent of their termination, run them as far as you can inside the split loom and have them exit right where they terminate. Looks good = IS good.

      My top 10 list of hints:
      1. Take your time.
      2. Make the harness on a bench. Only one wire per color allowed.
      3. No splices allowed mid wire. If a wire is too short, replace it with one of sufficient length.
      4. Speaking of sufficient length, 'tis far better to throw 2 feet of wire away than to be an inch short. Don't skimp.
      5. Place the harness in the boat and fasten it to the structure.
      6. Connect the ends where they go.
      7. Train the wires away from heat sources, sharp edges and moving parts.
      8. Make notes on your diagram for future reference.
      9. Sit back and bask in the glory of a job well done.
      10. Take pictures before and after for our admiration.


      edit:
      Here are before and after pictures of forum member Ezra Korts CAL 29. The engine rewiring took two of us a single day including sourcing the wire at the local chandler (San Diego) and a very nice lunch.
      Attached Files
      Last edited by ndutton; 11-19-2023, 03:04 PM. Reason: added pictures
      Neil
      1977 Catalina 30
      San Pedro, California
      prior boats 1987 Westsail 32, 1970 Catalina 22
      Had my hands in a few others

      Comment

      • Indy
        Senior Member
        • Oct 2014
        • 41

        #4
        Correct schematic?

        Hello!
        I have been working on this slowly, as time allows and am starting to draw up my wiring paths. A question that puzzles me about eliminating the ammeter and installing a voltmeter instead, is how now to connect the output of the alternator? Can it go directly to the same terminal on the solenoid as the battery cable?

        Comment

        • Dave Neptune
          Afourian MVP, Professor Emeritus
          • Jan 2007
          • 5115

          #5
          That will work however I like hooking it to the battery switch output side. That way you can charge one bank at a time or both at the same time. It will really work either way depending on how the wiring lead(1&2) go the the solenoid.

          Dave Neptune

          Comment

          • hanleyclifford
            Afourian MVP
            • Mar 2010
            • 7031

            #6
            The short answer is yes. But regarding the ammeter, I would think carefully about this. It depends on how you use the boat. If you just knock around locally day sailing in easy range of a tow or mechanical assistance you will be ok with just a voltmeter. But if you travel any distance and stop in a remote anchorage far from home it would be better to have both ammeter and voltmeter. A voltmeter can fool you into thinking a battery is ok because it could be showing you just a surface charge. The ammeter tells you what the battery is actually capable of. Dave is right about the stock ammeter; get rid of it. The Blue Seas System digital is the choice for cruisers. BTW, the shunt will go in the negative circuit near the battery.

            Comment

            • hanleyclifford
              Afourian MVP
              • Mar 2010
              • 7031

              #7
              Regarding your two pictures the following. That terminal block is a lot of unnecessary connections some of which could be introducing resistance. Neil has always advocated keeping connections to a minimum and I agree. I also understand the desirability of fabricating a harness on the bench but for most of us with complicated systems that is not possible. If you do get the wires out of that hole where the trailer connector is take some time to enlarge, finish and even grommet the hole for better protection of your new wires. Avoid introducing any new trailer plug type connectors unless they are marine rated.

              Comment

              • Indy
                Senior Member
                • Oct 2014
                • 41

                #8
                Originally posted by hanleyclifford View Post
                The short answer is yes. But regarding the ammeter, I would think carefully about this. It depends on how you use the boat. If you just knock around locally day sailing in easy range of a tow or mechanical assistance you will be ok with just a voltmeter. But if you travel any distance and stop in a remote anchorage far from home it would be better to have both ammeter and voltmeter. A voltmeter can fool you into thinking a battery is ok because it could be showing you just a surface charge. The ammeter tells you what the battery is actually capable of. Dave is right about the stock ammeter; get rid of it. The Blue Seas System digital is the choice for cruisers. BTW, the shunt will go in the negative circuit near the battery.
                Thank you for that advice. This is just an inland lake boat, so the ammeter is really overkill for what it will do for the rest of its useful life (or mine).

                Comment

                • Indy
                  Senior Member
                  • Oct 2014
                  • 41

                  #9
                  Originally posted by hanleyclifford View Post
                  Regarding your two pictures the following. That terminal block is a lot of unnecessary connections some of which could be introducing resistance. Neil has always advocated keeping connections to a minimum and I agree. I also understand the desirability of fabricating a harness on the bench but for most of us with complicated systems that is not possible. If you do get the wires out of that hole where the trailer connector is take some time to enlarge, finish and even grommet the hole for better protection of your new wires. Avoid introducing any new trailer plug type connectors unless they are marine rated.
                  And thanks for this as well. I have always assumed the terminal block is there because of some prior owner's messing around or upgrading the wiring harness and have considered just wiring directly from the panel to the various contacts on the motor, although with the difficulty of accessing anything onboard the motor, I could see the convenience of the terminal block if something goes wrong with a gauge later on. Even if the terminal block is included, the total length of wire from gauges to motor will only be about 3 feet, and in fact, the total wiring run will be reduced by many feet, since the prior owner had just coiled together and tacked a wiring harness onto the engine room ceiling. Currently, the wires all run from that terminal block through about 15 feet of wire, then to the old trailer plug (which is being eliminated, of course) and on to the gauges. This project is to mainly replace failing gauges and simplify for easy troubleshooting.

                  Comment

                  • sastanley
                    Afourian MVP
                    • Sep 2008
                    • 7040

                    #10
                    Indy, I did the same several years ago and also eliminated the ammeter and wired the alternator output as Dave recommended. It is just an additional larger cable (I used 4 gauge to match what the other large cables were)
                    I think my original ammeter was wired with 8 gauge.

                    I occasionally had to disconnect a wire or two, so I had a ground (-) block (smaller one to port), and terminal block near the engine for all the other non ground engine wire harness for convenience.

                    Later on, I added a nice Blue Seas negative side shunt ammeter and a voltmeter in my 12v DC electrical panel, as we did some longer term cruising as Hanley commented, but at least if you see 13.xx volts on your voltmeter you can be relatively confident the alternator is charging.
                    Edit - since you mentioned gauges, I basically terminated the other end in a similar fashion and added a tach & voltmeter while removing the ammeter..so here is a pic of that too.

                    maybe one of these days i will get a little neater with my work.
                    Attached Files
                    Last edited by sastanley; 03-26-2024, 06:51 PM.
                    -Shawn
                    "Holiday" - '89 Alura 35 #109
                    "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
                    sigpic

                    Comment

                    • Indy
                      Senior Member
                      • Oct 2014
                      • 41

                      #11
                      Originally posted by Dave Neptune View Post
                      That will work however I like hooking it to the battery switch output side. That way you can charge one bank at a time or both at the same time. It will really work either way depending on how the wiring lead(1&2) go the the solenoid.

                      Dave Neptune
                      Thanks for this- I am going to go directly to the solenoid post because it's just easiest at this point, plus I really don't know how much charge I get with the alternator, with only motoring in and out of the marina at low RPM. I have a solar panel that keeps the house bank charged and I will eventually re-wire so that I can charge either bank with it. For now, my immediate question is what size wire for that short (2 ft) connection between the alternator and solenoid, and what size fuse. I believe it's an original alternator, and will verify that when I check the boat. For what it's worth, the current wiring from the alternator to ammeter to bat on the Ign switch is 10 awg with no fuses. In fact, there are no fuses on any of the wires, except for the blower circuit, which I am addressing. But I'm wondering whether I can go with 10 awg, which is essentially what was used in the prior application and about five longer. Or do I need 8 awg? Or even, do I need to charge the battery from the alternator at all?
                      Last edited by Indy; 04-06-2024, 10:17 AM.

                      Comment

                      • Dave Neptune
                        Afourian MVP, Professor Emeritus
                        • Jan 2007
                        • 5115

                        #12
                        I used 8ga on mine during my rewire as I was planning on possibly going to a 50amp alt but never bothered. I did not need the oomph as I had no refrigeration and I converted my lighting to LED. I could sit for a week at Catalina and still start on the "house" circuit with the start still in reserve.

                        Larger wire especially for longer runs is just a good idea.

                        Dave Neptune

                        Comment

                        • Indy
                          Senior Member
                          • Oct 2014
                          • 41

                          #13
                          I found this diagram in an old thread- seems like what I'm trying to do here.
                          Any issues with following this for my re-wire?
                          Attached Files

                          Comment

                          • Dave Neptune
                            Afourian MVP, Professor Emeritus
                            • Jan 2007
                            • 5115

                            #14
                            That will work just fine. Best to put more time into thinking about future addons
                            and how to shorten runs before doing the actual wiring. Also remember to do as much as you can on buss bars for both positive and negative runs. And be sure you have a good ground of at least 4ga from the motor to the batteries.

                            Note, most all DC wiring issues turn out to be on the ground side so don't skimp there.

                            Neat, short and simple is best with good planning.

                            Dave Neptune

                            Comment

                            • Indy
                              Senior Member
                              • Oct 2014
                              • 41

                              #15
                              UPDATE: I completed the work, the engine starts, I didn't catch anything on fire and the gauges all work. Will post some pictures at some point soon.
                              Thanks to for the advice and suggestions!
                              Attached Files

                              Comment

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