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Thread: Need a little wiring help with a 74 Tr6

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    Need a little wiring help with a 74 Tr6

    We recently installed a new main wiring harness in our 74 Tr6. After install, I have two problems. The headlights won't dim with the dimmer switch. Also the interior lights won't turn off. I have working door switches including a lucar two connector switch on the drivers side. At least it test positive for continuity. Everything else on the car works perfect. at the end of the install I was left with one brown wire with a bullet end and one green and black wire with a bullet end. Both are located directly behind the ignition. I know the brown is for power, but not sure for what. I should also point out that the seatbelt module was removed last year when it failed so we use a jumper on the red and white and red and orange wires. Not sure if that is important here but wanted to point it out. Any help you guys could provide would be invaulable. Thanks!

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    Jedi Knight
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    Re: Need a little wiring help with a 74 Tr6

    Welcome to the forum. We'd like to see a few pics of your car.

    RE: "The headlights won't dim with the dimmer switch." That's unusual, even for a Triumph. What makes them dim?

    RE: "Everything else on the car works perfect." That's unusual, especially for a Triumph. Are you sure?

    RE: "I was left with one brown wire with a bullet end and one green and black wire with a bullet" I hope you have a working fire extinguisher in your car. (Sorry if my humor is not appreciated.) If you don't have a wiring diagram by now, you need to get one. They are available free from advanced wiring and other places. Be aware the diagrams are different from year to year. You should note the BROWN wires on a TR6 are wired directly to the battery. They are always hot and not fused. If that bare bullet end touches ground while you are bouncing down a country road, you could have a fire under your dash in less time than it takes to pull over and find your extinguisher. It needs to be covered or connected where it belongs, but somehow insulated.

    The Green/Black is the wire from the fuel gauge to the fuel sending unit. I don't know why it would be bundled with the ignition wires.

    Sorry I can't offer anything more helpful, but you need to be very careful with that loose brown wire.
    59 TR3A "Butter"

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    Jedi Knight smaceng's Avatar
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    Re: Need a little wiring help with a 74 Tr6

    Welcome!
    As the post above: www.advancedautowire.com has the wiring diagrams for the TR6....and select you year of 1974.
    Don't know about the brown wire with a bullet, but there is one brown wire which goes from #4 to #2 at the ignition switch.
    If your fuel gauge works, then maybe it is LIGHT Green with black which is a connection to the wiper/washer switch.
    Double down on the above comment that the Brown wire is always hot.....treat it like a firecracker.....keep it under control and covered.
    Also Try Dan Master book on TR6 wiring....excellant book
    Good luck, Scott in CA
    1973 TR6

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    Luke Skywalker
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    Re: Need a little wiring help with a 74 Tr6

    Good advice above on the Advanced Wire diagrams. Make sure both the dimmer switch and the rocker switch are wired correctly. I think they are both marked with numbers which correspond with colors on the diagram. Easy enough to test the brown for voltage and it is not too uncommon to find a dead endin a replacement harness, or an OE one for that matter.
    Tom
    1960 TR3A TS73117 (under restoration year 8, owned since 1964)
    1959 TR3A TS58023 (in case I never finish the one above)
    1969 Triumph Herald 13/60 (a whim)
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    Re: Need a little wiring help with a 74 Tr6

    By "dimming" I assume you mean low beams?

    A nice thing about electricity: if you wire it right, it works right. So, it's a safe bet there is a wiring error. Less likely is a bad switch, but it's possible--it's just unlikely that it just happened to fail right now.

    I think you need to get a wiring diagram and go through the circuits that are not working right. Especially, resolve those problems where you have a hanging lead and are not sure where it goes. That's likely to be part of your problem.
    Steve Maas
    1966 Triumph TR4A, undergoing restoration: http://www.nonlintec.com/tr4a
    1952 MG TD, restoration completed 2014, sold 2016: http://www.nonlintec.com/mgtd
    1960 Austin-Healey "Bugeye" Sprite, sold 2010: http://www.nonlintec.com/sprite
    1967 Porsche 912: http://www.nonlintec.com/porsche

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    Re: Need a little wiring help with a 74 Tr6

    Thanks for all the replies! I have both the brown and black with green stripe wire capped and taped for safety. I also pack a fire extinguisher everywhere too. We have Dan Master's wiring book which was pretty great on this job. We used the 74 wiring diagram quite a bit. I just couldn't locate those two wires on the diagram. Also above I said it was green and black. It is actually black with green. I will go back through the wiring for the dimmer (low beam) switch the next time I work on the car. We replaced the pull switch (under the radio) for the interior lights. The connections were different on the new switch. Does anyone know if it matters how those wires are hooked up? This is one spot I haven't worked on trying to fix the interior lights.

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    Re: Need a little wiring help with a 74 Tr6

    I had a chance to work on the car some today. The brown wire that isn't connected isn't part of the main wiring harness. It is coming from the dimmer(low beam) switch. Dan Master's wiring diagram has that wire running through a small rectangular box. Also coming out of that box are two purple wires that run to the key Illumination lamp and also the footwell lamp. Could this mean that both problems are related? Any one have any ideas on that rectangular box? Is it just a connector?

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