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Thread: Wiring up late model power seats in our tri-5's

  1. #1
    Registered Member WagonCrazy's Avatar
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    Wiring up late model power seats in our tri-5's

    So I have these bucket seats out of a 2002 Lexus SC430, going into my 57 nomad. They are power seats (but not heated). Starting to work on fabbing up custom floor mount brackets and got curious about what it's going to take to wire them up so I can adjust them.
    Searched Google high and low, and really couldn't come up with a usable wiring diagram.

    So I set one seat on the workbench, and saw there were about 8 thin gauge wires and 2 heavier gauge wires (all were cut from the floorpan out of the lexus.)

    Applied 12volt power to one heavy wire (blue) , and grounded the other heavy wire (black/white). Didn't bother to connect any of the others yet.

    Clipped a 12 volt trouble light to the ground wire, then started to probe the main connection between the seat switches and the seat controller unit under the seat) and each time I grounded a wire...a motor would turn.

    So...this thing works when a circuit gets grounded.
    I'm a bit out of my element here, but all up for the challenge of figuring out how to wire this seat up.

    Anyone got hints, clues or wiring diagrams to share here? How did you wire up your late model seats?
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  2. #2
    Registered Member chevynut's Avatar
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    Paul, do your seats have memory? It sounds like you should have a "black box" under your seat which is where all the controls are. The controller houses the relays to operate the seat. Your seat switch only grounds the inputs to the control box and the electronics in it operates the relays. My Lexus seats are similar, as are my Eldorado seats.

    I'm not sure I understand what your issue is if you can make the seat operate. Is the harness from the seat switch to the control box intact?

    Typically the passenger seat doesn't have a control box, and the switch supplies power directly to the motors. So if that's the case, you only have a power and ground connection to the seat.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  3. #3
    Registered Member WagonCrazy's Avatar
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    Paul, do your seats have memory? It sounds like you should have a "black box" under your seat which is where all the controls are.
    Yes, there is a black box mounted underside the seat.

    I'm not sure I understand what your issue is if you can make the seat operate. Is the harness from the seat switch to the control box intact?
    The harness from the seat switches to the control box is intact. But the switches do not operate the seat (when I have the main power and ground wires that come from the body harness to the seat hooked up)

    Maybe I'll hook it up again tomorrow when I get some time to shoot a short video, and post that to show how I got the seat motors to run.

    I haven't even looked under the passenger seat yet, but there are definately control switches on that seat as well.. I will study the wiring on that one as well and maybe it will shed some light on how to hook up the drivers seat.

    Just wanting to know what I need to expect when it comes time for wiring. For now, I'm just fabbing up the seat brackets to set the seats where I want them to mount, and get that part of the metal fabbing checked off the list. There's so much more to do on this thing.

    Glad to have found this tri-5 site (and a few others) because that's the inspiration I need to get solutions figured out with the help of all you guys who've gone before me.
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  4. #4
    Registered Member chevynut's Avatar
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    Paul, I have wiring diagrams for the Eldorado seats but I don't think I have any for my Lexus seats, although I might. Mine are older than 2002 also and they're from an SC300 or SC400. This is what my seats look like and I think they were used from 1991-2000.



    Did you know that the Lexus SC300/400/430 was also called the Toyota Soarer?

    I am betting your small wires are the ones that go to the memory switches on the driver's door. Did you ground the seat track when you tried the seat switches? Something needs to ground the seat to the battery for the seat switches to work. All the switches do is connect the specific input of the controller to ground. They may have a logic ground that's separate from the 12V ground.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  5. #5
    Registered Member chevynut's Avatar
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    Found this:

    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  6. #6
    Registered Member WagonCrazy's Avatar
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    Did you ground the seat track when you tried the seat switches? Something needs to ground the seat to the battery for the seat switches to work. All the switches do is connect the specific input of the controller to ground. They may have a logic ground that's separate from the 12V ground.
    I didn't ground the seat track when I tested it. So I'm guessing I will need to do that.
    Also, the drivers seat does have a memory controller, so thats' what all the other wires are for I'm guessing.
    So I'll need to figure out which of those other wires needs to be grounded, to see if that makes the switches work.

    As for the passenger seat, there are the same 2 heavy gauge wires (blue and black/white) and 3 other small gauge wires. Two of those are for the seatbelt indicator, and not yet sure what the last one is for. But when I hooked the 12v to the blue, and ground (from battery) to the black/white, the switches WORKED. So the passenger side is straightforward for wiring it up.

    And my seats look nearly identical to the one you show in your pic...
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  7. #7
    Registered Member chevynut's Avatar
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    Paul, I'm not sure grounding the seat track will make any difference, but it can't hurt anything. There should be a ground wire from the module to the seat switches, which is a logic ground. You could check the switch connections to make sure they're getting grounded when you push the switch.

    Read this...

    http://www.trifive.com/forums/showthread.php?t=36796
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  8. #8
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    Eldorado seat wiring diagram

    Quote Originally Posted by chevynut View Post
    Paul, I have wiring diagrams for the Eldorado seats but I don't think I have any for my Lexus seats, although I might. Mine are older than 2002 also and they're from an SC300 or SC400. This is what my seats look like and I think they were used from 1991-2000.



    Did you know that the Lexus SC300/400/430 was also called the Toyota Soarer?

    I am betting your small wires are the ones that go to the memory switches on the driver's door. Did you ground the seat track when you tried the seat switches? Something needs to ground the seat to the battery for the seat switches to work. All the switches do is connect the specific input of the controller to ground. They may have a logic ground that's separate from the 12V ground.
    Hello, new to site. I saw your post above from a few years ago. I have 99 Eldorado seats with memory for my 56 Nomad. I am having issues getting seat to work, I can power the motors individually but when I apply power to the main harness the switches will not work the seat. Do you still have the wiring diagram? That would be very helpful. Any help is greatly appreciated. Todd

  9. #9
    Registered Member chevynut's Avatar
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    Quote Originally Posted by Tcoe1955 View Post
    Hello, new to site. I saw your post above from a few years ago. I have 99 Eldorado seats with memory for my 56 Nomad. I am having issues getting seat to work, I can power the motors individually but when I apply power to the main harness the switches will not work the seat. Do you still have the wiring diagram? That would be very helpful. Any help is greatly appreciated. Todd
    Hi Todd,

    Please send me an e-mail through my website"contact us" link and I'll try to help you get your seats working. I have the same seats in my 56 Nomad. I have a bunch of wiring diagrams, but I think you have a simple wiring issue. Also, if you don't have them mounted yet I sell seat mount kits that make them a bolt-in deal....check them out on my website under "misc products":

    www.CLASSICEDGEDESIGNS.com
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  10. #10
    Registered Member Bihili's Avatar
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    As Chevynut said, include a relay and read up on logic ground wiring. It is a little confusing at first.
    Bill 1957-427-177-6-410

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