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Thread: Triumph tr3 overdrive wiring

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    Yoda
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    Triumph tr3 overdrive wiring

    Triumph tr3 overdrive wiring-- I am into uncharted territory and looking for a little guidance for the od wiring.

    My first question:

    How do I know what side is which on the switches on the top of transmission—one side black and one side yellow with a strip? Probably YP and the other B on my old harness—maybe it does not matter as long as they are same on both sides of both switches?

    Hooking up-- W1 – my wiring diagram suggest A3 at fuse box or “starter switch.” I wonder if that means the push switch for start (hot side) or the solenoid (always hot side) what is most commonly used?

    Hooking up--- C1—my wiring suggest control box A1-- or ammeter. What is most commonly used?

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    Obi Wan Sarastro's Avatar
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    Re: Triumph tr3 overdrive wiring

    Switch terminals don't matter. Just be sure each switch has one yellow wire connection and one black. Main concern is that you don't accidentally short out a switch. That would defeat the lockout.

    W1 goes to a source of switched power; i.e., switched on and off by the ignition switch. That is the ignition switch, the terminal of the fuse block that is switched by it, or the side of the starter switch that is connected to the ignition switch. This way the relay is powered only when the ignition is on.

    The C1 terminal is connected to something hot all the time. Since the A terminal of the box and one side of the ammeter are connected, it really doesn't matter which you use. Just be sure you get the right side of the ammeter, or you will get a big kick in it every time you turn the overdrive on, which is probably not what you want.
    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: Triumph tr3 overdrive wiring

    Thanks Steve, I really appreciate it--- that was a huge help. I am starting to see the big picture now. I totally freaked when I saw those switches with wires going into the transmission with hot and cold power. I did not realize that they stopped the trans from shifting when the overdrive is in use. Sometimes I have to be told.

    I picked up a couple of used overdrive switches and the wire coming out of the switch was gray. On the first one, I thought the gray wire was something someone added because the wire looked like lamp cord wire, but when I got the second one that one also had a piece of double gray wire on it. Have you seen the gray wire on the switch before?
    .
    I might go with A3 on the fuse box for W1 because the relay is on the back of the battery and I could go a long the battery box and out, but again I have a new harness and the wire would be outside. Same deal C1 that might be best going to A1 on the regulator rather than the Amp gauge behind the dash and let the wires show.

    My daughter lived in Long Beach. Her and couple of girlfriends found jobs as account receivable there, but she move last week to LA to be closer to work and less of a commute. She moved about a mile from this great Chinese restaurant called Mommy lu’s.
    Any thanks steve

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    Yoda CJD's Avatar
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    Re: Triumph tr3 overdrive wiring

    I used the starter switch and ameter, just because they were easier to reach rather than running all the way to the fuses.

    And...we’re going to need some pics soon, Steve!
    John

    1955 TR2

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    Yoda
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    Re: Triumph tr3 overdrive wiring

    Thanks John that was my first instinct. My master plan was to hook the wiring except the lights and start the car up and drive it outside and maybe around the block with the sheet metal off like doors and fenders and take some pictures. Well they say if you want to make God laugh—tell Him you plan. Anyways, the OD has me wiring in a few things, I did not figure on. I was spooking around the internet and found a few things from Randall, Geo, and John, but now I cannot find the one I want. So, John the one from you talked about running the wires through the hole in side of the cover. After the wires come out of the cover, do they go on floor then up to the relay? Plus, Geo suggested a fuse and Randall suggested diode. I am going to put diode in last because it looks like I can add it in and I have no idea what exactly I need, but Randall made it sound easy.

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    Obi Wan Sarastro's Avatar
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    Re: Triumph tr3 overdrive wiring

    One thing I forgot to mention--be sure that the gearshift is operating the switches correctly. There are thin spacers between the switch and the transmission to adjust this. If there are too many or too few, the switches will be always on or always off. You can check this with a test light or ohmmeter (switches disconnected, of course).
    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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    Yoda CJD's Avatar
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    Re: Triumph tr3 overdrive wiring

    Yes, once the wires come out of the grommet in the tunnel, then they go forward, coming out the top of the carpet, right by the relay. I actually built a harness with a sheathing to protect them from rubbing against the metal flooring as they run along the tunnel forward. Adding the diode is on my “to do list”. It is simply added across the appropriate terminals on the battery box relay.

    Somewhere near the grommet through the tunnel, the wires have a couple single bullet connectors, so you can remove the tunnel completely without having to disconnect all the wires. You just break them at the bullets. You can see these connectors on the “color” diagram that has been circulating...I think from Randall.
    John

    1955 TR2

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    Re: Triumph tr3 overdrive wiring

    Ok Steve, I tested them with an ohm meter and they are both open. The one switch has something like 2 shims that are perhaps seals and the other has 1. I can see a little oil around the one hole, so I assume the spacers are seal also. I am not sure how to check the switch as closed? I guess power on and a volt meter and then wiggle the shifter to see if they lock? I have the cover off because I inspected the gears and they looked good. Now I plan to drive it and see what it sounds and feels like. Heck John took his transmission apart and fixed it first. Because of my very limited knowledge of ODs, I am going at it from the other direction.

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    Re: Triumph tr3 overdrive wiring

    Do you have the transmission in gear? Switches close when in 2nd, 3rd, or 4th gear. In 1st or [thank God] in Reverse, as well as neutral, they are open so OD doesn't engage.

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    Re: Triumph tr3 overdrive wiring

    I am going to use the back half of the original wiring harnesses for OD and the gauge looks like 14 or 16. I need to make the wires from the relay to power. What size wire can or should be used for that? I have plenty of 16 in a few colors, is that too small of gauge? The runs are short just a couple of feet.
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