Wiring a trailer connection for can bus cars !
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  1. #1
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    Default Wiring a trailer connection for can bus cars !

    Hi
    Here is an article about wiring a trailer connection into a late model car, a Pug with a can bus, without having to give up a kidney to the Stealers for it,
    AutoSpeed - Towbar Electronics
    Julian know what he is talking about and the explanation is good.

    jaahn
    Worth a stickey ??

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  2. #2
    1000+ Posts robmac's Avatar
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    I used a similar approach a few years ago for a mate with a Japanese car which had multiplex wiring.

    However, I used SSRs (solid state relays) instead of the mechanical relays used by Julian.

    Solid State Relay SSR DC DC 10A 3 32VDC 5 220VDC | eBay

    SSRs have the benefit of only drawing 15 milliamps odd from the existing light circuits and don't have a coil as such and therefore have no inductive spike.

    SSRs have no moving parts and accordingly promise to more reliable that sh!tty Chinese relays. Especially when switching a brake light circuit.

    edit: If the vehicle is one of these modern soft roads, quite often the tailgates are electrically operated and have a meaty 12v+ feed to local controller. This is a great place to pick up the power feed to the devices.

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    1000+ Posts REN TIN TIN's Avatar
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    Why bother to make your own when you can buy a CANBUS relay so cheap now.
    I bought a CANBUS relay from the UK on Ebay for about $40 including delivery.
    By the time you buy 5 or more relays, fuse holder, circuit board, etc. it works out nearly the same.
    By memory, it's around $5 per relay from Jaycar. The switching relays are even more so it's about line-ball.

    After I bought the thing a Renault dealer assured me I don't need a relay for the JA Scenic. The Renault factory towbar wiring was just connected to the harness with scotchlock connectors. Their exact words "We've been fitting them without bypass relays for years and never had any problems". Not recommending you don't use a bypass relay, just shop around because it may not be worth making your own.

    Cheers
    Ren
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure. Mark Twain"

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    Default Relay the information !

    Hi
    I came across this article while looking for something else. I thought it may be useful for people with modern cars which do need a relay system, and who have limited electrical experience, and have been quoted a ridiculous price by a stealer or indeed have been knocked back by a regular towbar fitter. The article looked good and useful.

    As Robmac says, electronic relays may be a bit better, available at Jaycar also, but the ones in the article will work OK. Perhaps REN TIN TIN's car does not need a relay set but a rapidly growing number do, and not everyone will order a multi relay unit from England due to lack of confidence. Why are they impossible to find here ??? Conspiracy or what

    Jaahn

  5. #5
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by REN TIN TIN View Post
    Why bother to make your own when you can buy a CANBUS relay so cheap now. ...

    Cheers
    Ren
    You make your on relay interface when:

    The vehicle uses mobd bus ( proprietry toyota, which was my reason)

    or

    When you can't wait for an ebay seller to deliver a product which may or may not be suitable.

    Julian's solution is elegant because it will work with any vehicle with any bus communication system

  6. #6
    Real cars have hydraulics DoubleChevron's Avatar
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    Just buy a wiring bypass kit. It's a bunch of relays that act just as Robmac describes.

    wiring bypass kit | eBay

    Easy to fit, and safe... without any messing around with circuit boards/relays/etc...

    seeya,
    Shane L.
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  7. #7
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by DoubleChevron View Post
    Just buy a wiring bypass kit. It's a bunch of relays that act just as Robmac describes.

    wiring bypass kit | eBay

    seeya,
    Shane L.
    The reason I prefer solid state relays is because the brake lights are turned on/off a lot and the indicators are a cycled, ie flashed.

    Rapidly cycled on/off operation is not ideal for a mechanical device. Consider indicators on for a couple minutes waiting to turn the corner and the number of times the relay will turn on/off. I'd suggest a mechanical relay will fail quite fast. SSRs have no moving parts. Remember the relay coils are always powered - with or without a trailer plugging in.

    I chose the SSR in the package because no circuit board is needed and all connections are crimped lugs- fast and reliable. Just screw them to an aluminium bracket (wise to have a little heatsink) and mount behind the boot trim. Easy to fit, and safe... without any messing around with circuit boards/solder in relays/etc...

    At 4x $8 the cost justifies the lack of stuffing around. You could do the same job with four power mosfets (metal oxide field effect transistor) at a couple of dollars each. But by the time it is built on circuit board and the mosfets heat sinked you loose the cost benefit to time.

    The off the shelf SSRs are bullet proof and reliable as well. At $8 a couple of spares are justified.
    Last edited by robmac; 17th March 2014 at 03:51 PM.

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    1000+ Posts Haakon's Avatar
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