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Testing wires

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  • Testing wires

    About ready to redo the wiring on the old boat. I first want to trace my panel main ground since this project appears to have some confusion under the cloak of sheathing. I don't have a multimeter, but have a cheap 12v tester from HFT.

    Before I disassembled the old console panel, one black wire was jumped to the switches and not working fuel gauge(I have fuel diagram)

    Nothing is connected to a battery yet. I first want to connect the engine red and black only. At that point, what do I need to do to check the black ground at the panel to see if this connection supplies my panel main grounding using this tester?

    The tester is a CEN-TECH circuit tester, has a single probe and a cord with a clamp. The instructions ask to connect the clamp to the battery post(NEG in this case) and touch the wire(main black at panel) with the probe tip. If it lights up, then OK.

    Sound right?

    This is an old boat with some confusion, sheathed runs, unidentified wires, odd colors in odd places, and about every issue that requires tracing before connecting.

    Please keep in mind this boat at the battery does not have a common place(buss) where a collection of grounds are obvious. Instead, the grounds for the bilge, fuel tank, and stern light disappear into a merging highway of cable and are probably spliced into the wire leading to the panel, I hope.

    Funny thing, the bow light ground flows toward the panel, but disappears also into a cable run, so somewhere under cover is a collection of spliced grounds??


  • #2
    Re: Testing wires

    That is a voltage tester and is typically used to test circuits OTHER than ground. With the light connected to ground, putting the probe on the other end of a ground circuit would not work since there is no current flow. However, you can do it this way:

    1) Connect the clip to the POSITIVE terminal on the battery.
    2) DISCONNECT the ground wire from wherever you want to test it.
    3) Touch the probe to that wire.
    4) Light lights, you have a ground. No light = no ground.

    Keep in mind that your boat probably has two smaller gauge wires (probably #8 or #10 gauge) that run from the battery to the helm. If not, all power runs through the engine harness.

    Comment



    • #3
      Re: Testing wires

      Thanks, will try that. I do have a red wire that connects to the battery, and into a circuit breaker, then will test the red wire at the panel to see if that is my panel feed. It does not have a separate ground to match which led me to think that the panel ground is coming from the engine ground?

      In other words two red and one black on the battery. If your method works, it will confirm my panel ground is spliced in somewhere through the engine connection to the main battery.

      If so, then can I use your method to trace other wires?

      Assume the test concludes that the panel ground and the panel main red feed work when the engine red and black, plus the additional red are connected to the battery. That gives me power and ground to finish wiring the panel which has a brand new pre-wired 5 switch with breaker/fuse built in. All I would need is to follow their instructions to join the colored wires for bilges, horn, NAV, and courtesy lights.

      The kit also includes a ground bus. The instructions say to connect the main black to the bus, then the black from each switch to the bus.

      My speedo is a pitot, and only one white wire attached to it. I figure this is the backlight, and would splice power of the bow light feed so it lights only when the bow light is on. How do I make sure that white wire is backlight?

      The current wiring of the fuel tank is odd. I have the diagram generously provided on this site. I have the pink wire at the panel, and will follow the diagram for the fuel gauge except there is no solid evidence of IGN feed to the panel to complete the wiring so it only reads when the key is in the ON position. I will light it though like the speedo light. Question:

      If the fuel gauge has to get power from the same source as panel switches, what draw on the battery is there, and is it significant to drain the battery in a short time? There is also one additional red wire at the panel, looks newer than 30 years old, looks like it was snipped clean or never used. How would I trace this red wire to its source? Could it be the IGN feed I need for the gauge?

      Don't mean to ramble.

      If I connect as described, test the other unused red wire and it is not hot, then turn the IGN switch to ON, then test again, it would light if it was the IGN feed?

      Comment



      • #4
        Re: Testing wires

        I can assure you that if you do not have a ground wire from the helm to the battery that ground MUST be obtained through the engine harness which is a NO-NO. Yes it works, but that harness probably does not contain a #8 or #10 ground wire. Ground wires MUST be the same size or larger than the red wire (positive) that feeds a circuit. Besides, a failure anywhere in the engine harness means every accessory on the boat dies including a marine radio so you lose communication in an emergency.

        As as I said, the tester you have is typcially used to test OTHER than ground. The procedure I posted is to test for the GROUND wire. DO NOT use that process to test OTHER than ground. To test those circuits you connect the clip to the NEGATIVE terminal of the battery and then touch the other circuits to see if voltage is present.

        Comment



        • #5
          Re: Testing wires

          Sounds like you a mess of confusion!

          Disconnect the engine harness and battery connections
          One thing I have use to trace wires:

          Use a 9v battery, they don't have enough current to hurt much but will help show 'continuity'.

          As previously posted, connecting the test light leads backwards can be used to check for common ground wires.

          One thing I would suggest, if you're re-doing the wiring, DON'T TRY TO FIGURE OUT WHAT IS THERE...you could spend hours trying to figure out IT'S ALL WRONG...old boats had everybody and their mother try their handy-work.....take plenty of notes, use masking tape and perminant marker to mark connections and remove EVERYTHING, start un-doing all the tape/connections and 'other stuff'......remove the mystery, sheathed runs, unidentified wires, odd colors in odd places, merging highway of cable and start over.

          http://forums.iboats.com/showthread.php?t=186986

          Nice looking boat/project!

          Comment



          • #6
            Re: Testing wires

            Understand, maybe I am making this sound like a mess when it isn't.

            The initial confusion is from a basic concern of electricity. Always led to believe one red and one black.

            If I have an engine red and black, and a trim motor red and black, then I should have a panel red and black. The only way to find out how the panel was grounded is to trace back where the single black wire at the panel originates.

            One would think very near to the red wire at the battery that runs through a 15amp breaker. I am also sure somewhere it is joined with the anchor light, bilge, and fuel tank grounds.

            I can simply run a brand new black wire from the battery to the panel, by doing that, I need to locate the grounds for the aforementioned items to get them grounded.

            I am not going to rip apart all the wiring because all indications show only the fuel tank/gauge wiring was botched.

            Comment



            • #7
              Re: Testing wires

              Originally posted by Silvertip View Post
              That is a voltage tester and is typically used to test circuits OTHER than ground. With the light connected to ground, putting the probe on the other end of a ground circuit would not work since there is no current flow. However, you can do it this way:

              1) Connect the clip to the POSITIVE terminal on the battery.
              2) DISCONNECT the ground wire from wherever you want to test it.
              3) Touch the probe to that wire.
              4) Light lights, you have a ground. No light = no ground.

              Keep in mind that your boat probably has two smaller gauge wires (probably #8 or #10 gauge) that run from the battery to the helm. If not, all power runs through the engine harness.
              Do I need to connect the red/black engine wires to the battery first?

              Here is basic inventory of what the boat has. Disregarding anything that gets connected with an inline direct to the battery such as VHF and a fish finder, the following core wiring exists:

              At the main battery, a red/black to the engine, a red/black to the trim motor, and a red connected to a 15 amp breaker that should test out as my feed to the panel.

              The trim controls have a 3 way wire from the control box to the trim motor(blue-green-purple)

              At the panel is a black wire, a red wire(more reddish orange and matches the color at the battery breaker), a pink sender wire, a brown bilge wire, a browinsh horn wire, blue and green NAV light wires, and another mysterious red wire clean cut and/or never used?

              Connected(riding along) with the red wire at the battery that appears to be my panel feed is a purple wire and a white with green stripe wire. Not sure how these were connected at purchase but they have post rings.

              Coming from the fuel tank is a harness that starts with a black wire and a pink sender on the female side of the clip. Also coming out of that female side is a blue wire that has a clamp on it and was at one time connected to the battery, guessing the negative post. On the male side of the clip is the continuation of the pink sender, black ground, and white with green stripe.

              The only wire that makes it to the panel is the pink sender. Where did the black ground terminate and where did the white with green stripe wire terminate.

              The 3 main items that cause the confusion are the panel ground, the fuel harness, and the purple wire in the trio at the battery.

              If you have one-half of a harness connection that includes 3 wires, one black acting as a ground to the fuel tank, one pink sender, and one blue wire, and that blue wire finds its way to the negative battery post, can this be construed as the blue connecting the ground to the tank and sender?

              If on the other half of that harness is a pink sender, a black ground, and a mysterious white wire with green stripe, does this harness continue the flow as described? Can this black be the ground at the panel via the blue wire connection to the NEG post, to the tank, and forward to the helm?



              As far as the purple wire, someone mentioned that the 1979 Merc tilt/trim used its own power system for IGN, and stated that was how the up/down/trailer was fed. If that ends up being accurate, that leaves the matching white with green stripe wire of the trio unanswered, but curious as to why the same color is involved with the fuel harness?

              If that wire appeared at the helm as an odd way of powering up the fuel gauge directly, then I wouldn't understand that scheme.

              Thus, it is a process of elimination trying to avoid trial and error and the use of some type of tester and in need of the best tracing procedure.

              Comment



              • #8
                Re: Testing wires

                OK, picked up an inexpensive digital Multimeter, now what?

                First want to check the panel feeds. In other words, connect what I think is the red to the battery and wacky misdirected ground also. At the panel, I have the red and black wires and want to see if these are my panel source of power and ground. I suppose I set the meter to 20 on the V side and probe red to red and black to black?

                Let's say it reads 12 volts or something in that range. Does this mean I have found the correct battery connection to the panel?

                Next, disconnect my battery and go OHMS

                How do I use this Multimeter to trace wires? Considering each end of the wire is further than the probes can reach, what use is this device? These look like they are best for PC boards!!

                I have read various tutorials and it seems they don't apply to what I am trying to solve.

                Can someone also shed light on why certain boat harnesses have different colors on each side of the connector clamp, and often times more on one side, less wires on the other? Why would they change?

                In the meanwhile, gonna return this device and get a porcelain light fixture instead.............lol

                Comment



                • #9
                  Re: Testing wires

                  Resistance (Ohms) Testing: Set the selector to Rx1. To test a single run of wire you need to make sure there is nothing else connected to that circuit along the line. This is a simple end to end test of a single length of wire (say the "S" (sender) wire from the fuel tank sender to the "S" terminal on the gauge. To test that wire you would disconnect the EITHER the tank end or the OR the gauge end. Touch one probe to the gauge end and the other to the tank end. Probes too short and wonder what to do? Come on Dude, add a length of wire from your junk box so the probe will reach. Continuity will register on the meter whether digital or analog. WARNING: DO NOT attempt resistance measurements on a powered circuit. Power must be removed.

                  Voltage: The negative probe goes to ground. Positive probe goes to the point under test. This test tells you THAT particular point has 12 volts. It doesn't tell you how it is getting there. It also tells you that the pont at which the negative probe is connected is GROUND. Like above, it does not tell you how it got there from the the battery. You either follow the wires from one end to the source of 12 volts and ground, or you use the the RESITANCE (continuity) checks to determine which wire is which if you can't trace them visually.

                  Comment



                  • #10
                    Re: Testing wires

                    will try, I drew up the wiring but can't get the picture uploaded due to system changes??

                    Comment



                    • #11
                      Re: Testing wires

                      Originally posted by Silvertip View Post
                      Voltage: The negative probe goes to ground. Positive probe goes to the point under test. This test tells you THAT particular point has 12 volts. It doesn't tell you how it is getting there. It also tells you that the pont at which the negative probe is connected is GROUND. Like above, it does not tell you how it got there from the the battery. You either follow the wires from one end to the source of 12 volts and ground, or you use the the RESITANCE (continuity) checks to determine which wire is which if you can't trace them visually.
                      If I am trying to isolate which black wire, and I have the one end at the helm, under the resistance test, doesn't the opposite end need to be attached, to say the negative post, or just test both ends of each wire? In other words, If I had a length of wire open on both ends, just put one probe on side A and the other on side B, and the meter will tell it is continuous?

                      Comment



                      • #12
                        Re: Testing wires

                        You can start by testing to the battery negative post but your going to need to disconnect the wires connected to the negative post to isolate the wire your trying to identify, your looking for the lowest number of ohms possible, some DVM's have an audible alert on the diode function that you can use to identify wires when your alone just hook up to both ends and listen for the beep, but if your testing continuity you want a value to tell you if not only this is the wire your looking for but also that the wire is in good electrical condition.

                        Make sure your skin is not touching the probe leads metal surfaces it will not hurt you but it will read the resistance in your body and possibly mess up your readings
                        2000 Crownline 248 BR
                        454 MPI Bravo III
                        "Wet Lipps II"
                        2006 Dodge CTD 3500 4X4 Bighorn Edition
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                        Comment



                        • #13
                          Re: Testing wires

                          When using the RESISTANCE (ohms) method for testing continuity of a wire the battery inside the meter provides the power which is why you ALWAYS work in this mode with power OFF and one end of the wire disconnected. Yes -- this is an end-to-end test of a given wire so you simply touch each end. As I said before, one end or the other needs to be disconnected so there is nothing else in the circuit.

                          Comment



                          • #14
                            Re: Testing wires

                            Thanks Silvertip, yes, I figured I would have to attach extension wires to the probes.

                            So I did a basic test for OHM on a small piece of wire. Zero when in contact, and some other value when one probe removed.

                            Going to start on the two panel wires first. The main red should(or better) relate to the one by the battery that runs through the 15 amp breaker.

                            Question though. When I test the black main ground at the panel, and place the other probe on what I believe may be the end run of a junctioning of accessory grounds, and I get a ZERO reading, could that be a reliable conclusion to move forward, or does the conjunction of several black wires tied into one that will eventually get attached to the NEG later on have flaws? Or is this splicing just "in lieu of" using a ground bus in the rear of the boat?

                            Using this device, will it work on my mystery wires? If I have the visible end of a wire, what method would you use with it to find where it terminates, or leads to if they get lost in some cabled run?

                            Comment



                            • #15
                              Re: Testing wires

                              As I said before -- a resistance check is POINT-TO-POINT. If measures the continuity of the wire or the resistance of an object that is located BETWEEN the two probes. It cannot measure anything beyond either probe. Splicing is the same thing as having two, three, or a hundred wires all attached at a buss bar. A buss bar is equivalent to a piece of wire, a glob of solder, a crimp connection, or any other way of attaching group of wires to each other.

                              If you don't now where one end of a wire terminates, you also have no idea if there is anything connected along a wire you want to test so you need to be very methodical in your testing. Current needs to flow from the battery, to an accessory, and back over a ground connection to the battery. If there are branches feeding other things or grounding other things you need to identify those. The meter or test light cannot identify those for you. It can only prove or disprove what you know exists.

                              You don't need the meter to determine if the helm is getting power from the red wire attached at the battery. Disconnect it and if power goes away from accessories, the answer is yes. If they continue to operate, that wire is not the +12 volt supply. Since you KNOW (or at least reasonably certain) this is the case, why not disconnect the ground at the helm and simply run a new ground back to the battery so the existing red and new black wire are the feed and return. Problem solved, no meter or test light indicated. The existing ground for all accessories being run through the engine harness is simply a bad idea.

                              Comment

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