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1976 Alternator Upgrade

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  • 1976 Alternator Upgrade

    I upgraded my '76 TR6 Alternator from a Lucas model to a 13107N Model that many people have used. I also recently installed the Patton TBI and plugged in my laptop to datalog a driving session. I am getting below battery voltage which seems to indicate that the alternator isn't charging the battery while driving. I have read over quite a few post on the subject but still need help. I disconnected the alternator plug from the new alternator and checked the 2 wires in the plug to see if they were getting any power. The larger brown wire is getting 14.6 or so, but the smaller brown/yellow is at 0. The extra brown wire (that most people just tie off) is showing about 14.5 or so. I am trying to figure out why the smaller brown/yellow wire isn't showing any power, and if this is the reason that the alternator may not be charging the battery. The diagram from the DM Handbook shows 4 brown wires at the block between the battery and starter - however, I only have 3 wires. Any help would be appreciated - electrical is not my forte. Here are a few pictures of what I have:


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    1976 Triumph TR6 CF51693U
    HVDA 5-Speed / Patton TBI
    Hardtop / Miata Seats
    Live Axle

  • #2
    I too upgraded my 1973 to the 13107N Alternator and it has worked fine for the last 8 months. You may or may not know, the ignition light is a necessary component in getting your alternator to start charging. Battery voltage is supplied to the white wire to the ignition lamp at start up, it glows red as there is no voltage on the other side of the ignition lamp from the brown/yellow wire connected to the alternator. Once the alternator starts to spin, the battery voltage energizes the alternator's field coils through the ignition light, and the alternator starts producing voltage through the large brown wire. Once that happens, the ignition lamp turns off, as both sides now have full alternator voltage applied. Sometimes it is necessary to rev the engine a bit after start up to get the ignition light to go off and the alternator charging. So make sure the ignition light works and is not an LED, as sometimes that creates problems.
    The extra large brown wire from the main brown wire block is just an extra wire to the alternator which is not really needed.
    Hope that helps!
    Scott in CA
    1973 TR6

    Comment


    • #3
      Thanks for the reply Scott. I will double-check the ignition light tonight when I get home. I didn't realize the ignition light functioned like you explained. After installing the TBI, I have consistently had an issue with low voltage. I thought the Lucas alternator had gone bad so I went with the newer replacement. I even bought one of the testers to show if there is a problem with the battery or alternator, and it shows everything is fine. I thought I must have a damaged wire somewhere or something not connected well. I tried to clean all of the connections to make sure everything is metal-to-metal. The extra brown wire that was previously hooked to the Lucas unit - do you know if it correct to leave it tied off as I have it? There really isn't anywhere to hook it that I can see.
      1976 Triumph TR6 CF51693U
      HVDA 5-Speed / Patton TBI
      Hardtop / Miata Seats
      Live Axle

      Comment


      • #4
        Looks like your plug is missing the second brown wire (see picture of AAW wiring diagram), is this the one you say is “tied back”. If so, I would order the plug kit from Moss or another vendor and restablish it. I would recommend having that second brown wire connected as per the diagram, specially with the uprated 13107 output. Don’t know if that is the cause of your problem or not but a second wire to handle to the amps when charging is a good idea.

        You say that your low voltage situation started when you installed the Patton TBI, have to communicated with Rick about it? Maybe he has heard of this before and can help troubleshoot. Not knowing how it hooks up, there is not much I can do to help troubleshoot that.

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        Attached Files
        Last edited by lfmTR4; 01-07-2019, 02:43 PM.
        I72 Pimento w/overdrive

        Comment


        • #5
          14.v indicates to me that the battery is good and strong, maybe overcharged.

          With the car off, check the voltage across the battery posts.

          Start the car, and while running, again check the battery voltage across the posts.

          If while running, the voltage is 13v or greater, then the alternator is charging.

          If the voltage across the posts are equal, or lower when running, then the battery may not be being charged by the alternator?.

          Remove, check and clean all connections
          - at the terminal along the pos battery cable (if I recall, one of those connections had a pigtail smaller wire paralleled off of it - maybe only used by the stock alt)
          - remove and clean both battery terminal/posts
          - check that the ground cable is attached in two places, firewall and bell housing.

          Newer aftermarket alternators may not functionally use the smaller connection.
          Last edited by tr6harris; 01-07-2019, 11:36 PM.
          '74 TR6 CF13007U aka "Mr. T"
          Custom Blue (Delft-Like) and New Tan (Formerly Mallard and New Tan)
          Points, Ballast Bypassed, Bosch Blue Coil, Moss Cobalt Wires, Champion RN12YC plugs.
          Peaks and tweaks, but the spirit of Original
          Redlines always.
          My wife is the Driver, I'm just the Mechanic....

          Comment


          • #6
            +1 on Lou's comment. If the Triumph engineers put two heavy wires in the alternator plug for a normal output alternator, then that means the current outflow from the alternator can be challenging to the wire gauge used on a single wire. If you upgrade the alternator, you are potentially passing more current through the brown wire than it was intended to handle. I posted the chart below before - be sure you have enough wire for the job (hint - look at the size of the wire going to the starter!)


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            1976 TR-6 BRG - CF57239U
            Carbs by Poolboy
            Rear Camber Kit, Rear Hubs by Goodparts
            Gear Reduction Starter by TSI
            Distributor by British Vacuum

            Comment


            • #7
              Thanks for the additional info. I went ahead and ordered a new a new plug kit for the alternator from Moss just to make sure that isn't the problem. I also ordered a new positive battery wire since mine didn't appear to be in the best shape. I cleaned each of the terminals to make sure I am getting good connections. From what I have read, adding the second wire as tr6harris indicated seems to be in order with the modern alternator. I can add the wire in the new fitting on the alternator side, but does anyone have any recommendations where might be the best place to wire it in at the other end? Should I splice it in the existing brown wire or completely run the new wire to the block on the positive battery wire pictured below? It looks like I currently have three wires plugged into that block, but there is space for one more.
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              Attached Files
              1976 Triumph TR6 CF51693U
              HVDA 5-Speed / Patton TBI
              Hardtop / Miata Seats
              Live Axle

              Comment


              • #8
                As posted below. I ran a second 8 gauge wire from the alternator to the starter as in my car, it goes from there to the battery . I taped the two together to look as one harness.
                I72 Pimento w/overdrive

                Comment


                • #9
                  If Irecall the 13107 alternator is rated at 55A, the original Lucas at 35A.

                  My 13107 is on the stock harness, no mods.

                  Without reading the voltage across the battery at rest and when running, I am not convinced that your alternator is not charging.

                  Is the IGN bulb glowing when running or something?
                  '74 TR6 CF13007U aka "Mr. T"
                  Custom Blue (Delft-Like) and New Tan (Formerly Mallard and New Tan)
                  Points, Ballast Bypassed, Bosch Blue Coil, Moss Cobalt Wires, Champion RN12YC plugs.
                  Peaks and tweaks, but the spirit of Original
                  Redlines always.
                  My wife is the Driver, I'm just the Mechanic....

                  Comment


                  • #10
                    You are correct on the 13107 rating. I thought the same thing - that I could just hook it up and use the existing wiring without any issues. The IGN bulb doesn't stay on. I hooked it up to a battery charger and let it sit overnight. I did check the battery by itself last night (optimal) and it read about 13.6 without the car running. I started it up and checked it again with the car running and it was about the same - 13.4-13.6. It doesn't look like the alternator is is charging. The voltmeter in the car is showing about 12v. Since I installed the Patton TBI, I have data-logged it a couple of times and it consistently reads lower than it should - around 12v each time. Rick thought I must have something else running since it looks to be running just on battery power. I have not run it yet with the headlights on, but I do have an electric fan that kicks on. The voltage can affect the TBI system and the last time I ran the car, it ran poorly - stumbled quite a bit. It had never done that before. I am going to replace the alternator plug this weekend and run a second 8 gauge from the extra plug to the starter to see if it makes a difference.
                    1976 Triumph TR6 CF51693U
                    HVDA 5-Speed / Patton TBI
                    Hardtop / Miata Seats
                    Live Axle

                    Comment


                    • #11
                      Battery and Alternator sounds fine to me.

                      13.6 volts is strong (12.8v) is typical. 13.6 tells me that the alternator has no need to charge with the battery at that level.

                      I'd positively remove and clean all connections, especially the brown wires and the terminal block along the positive battery cable. (if not already)

                      I dont think changing the connector will make any difference....

                      CLEAN and tight is the order of the day..

                      How/where is the Patton gadget connected to read voltage?
                      Last edited by tr6harris; 01-09-2019, 10:26 PM.
                      '74 TR6 CF13007U aka "Mr. T"
                      Custom Blue (Delft-Like) and New Tan (Formerly Mallard and New Tan)
                      Points, Ballast Bypassed, Bosch Blue Coil, Moss Cobalt Wires, Champion RN12YC plugs.
                      Peaks and tweaks, but the spirit of Original
                      Redlines always.
                      My wife is the Driver, I'm just the Mechanic....

                      Comment


                      • #12
                        Cleaned all of the connections and everything is tight. I'm going to take it for a ride when I get home today and see if that helps. I did order the new positive battery cable and the new alternator connector if it doesn't. I'm not exactly sure how the TBI system reads the battery voltage, but there is a spot in the data-logging screen that shows it. When I sent it to Rick, he could see there the voltage was a bit low.
                        Here is a sample shot of the log that it records:

                        Click image for larger version

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                        Attached Files
                        1976 Triumph TR6 CF51693U
                        HVDA 5-Speed / Patton TBI
                        Hardtop / Miata Seats
                        Live Axle

                        Comment


                        • #13
                          You while you're out, take it to the FLAPS and have them load test it. They can do the alternator with the engine running if the clerk knows what he is doing. You can add to the load by turning on headlights, blower, etc. With the engine off they can test the battery.
                          I72 Pimento w/overdrive

                          Comment


                          • #14
                            Update: went out for a drive this afternoon and stopped by a FLAPS. Had them test my brand new 13107N Alternator while running and it showed a problem. I went back home and took the alternator off and then took it back to the store to have them test it. Sure enough, it failed. RockAuto will not replace it because I used it on a car other than what it was designed for - 1980 Ford Fiesta - so I am going to try to find one tomorrow to install and try again. Hopefully, this means that the wiring is good and I don't have to mess with all that. The battery is a new Optima, so I know it is good. I will update again once I reinstall the new one.
                            1976 Triumph TR6 CF51693U
                            HVDA 5-Speed / Patton TBI
                            Hardtop / Miata Seats
                            Live Axle

                            Comment


                            • #15
                              You mean you told them it wasn’t out of 1980 Fiesta? How would they know? I think I would try again with a different clerk now that you ‘now what car it came out of. That’s BS on not warranting because it wasn’t in the car it was designed for, the fact is it failed prematurely and they are just looking for excuses.
                              I72 Pimento w/overdrive

                              Comment

                              1976 Alternator Upgrade

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