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Towbar electrics wiring (relay bypass, not genuine)

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  • Towbar electrics wiring (relay bypass, not genuine)

    Hi guys

    So I finally got around to installing my towbar electrics that I got from Towbars Direct (Towbars Direct | Witter Towbar Systems, Tow-Trust Towbars, Westfalia Automotive, Thule Towing Systems (Brink), Bosal, GDW, PCT Automotive, Westfalia Monoflex, Westfalia SIARR) in the UK. I ordered the "Single Electric Kit (12N) with Multiplex By-Pass Interface Relay" for just £26.45. They won't ship to Australia, so I had them ship to a mate who then forwarded it to me. Ended up costing me a total of about $50 for the unit and getting it sent to me - BARGAIN!



    I was pretty worried about doing the wiring and getting the scotch locks on properly and onto the correct wires. Thankfully I had access to Elsawin so I could check up on which wires were the correct ones to tap. Removing the rear lights is very simple if you have a torx screwdriver set to remove the 2 screws holding each light in. There is a 4 pin plug that has 2 catches on it that you need to release the plug from the light units.

    On the right hand side I tapped 3 of the wires. The plug has numbered pins to make things easier, as well as the colour coded wires. On the right hand side they are as follows:
    Pin 1 - Black and Yellow - Tail light
    Pin 2 - Black and Green - Right Indicator
    Pin 3 - Black and Purple - Brake light
    Pin 4 - Brown - Earth



    On the left hand side I only tapped 1 wire - the indicator. On the left hand side the wiring is as follows:
    Pin 1 - Brown - Earth
    Pin 2 - Black and Red - Brake light
    Pin 3 - Black and White - Left Indicator
    Pin 4 - Black and Yellow - Tail light



    Testing the above wiring my tail light (when lights are on), brake light (when brake pedal is depressed), and left and right indicators work perfectly. I don't have reverse lights or side lights on my little trailer so haven't bothered trying to wire them yet. I probably should at some stage, but I am happy for now. At the moment I am powering the unit off the 12V supply in the boot - again, I'll investigate alternative options at some stage but for now I am happy.

    Hope those of you that are looking for an alternative find this useful. it's cheap and it works. Of course, it does not have the trailer stability program that the OEM wiring harness does, so the caveats that go with that apply if you go this route. I have a tiny little motorcycle trailer so don't feel I need it.
    sigpic
    Tiguan TDI, 6spd Tiptronic Auto
    Black, sunroof, comfort pack, off-road tech, tan leather, park assist & roof bars.
    Avg 7.63L/100km over 189,000kms

  • #2
    Now that you have confirmed it works please remove those horrid scotch locks and solder the wires on! If traveling on rough road it will give you problems in the end. If not at least wrap them in electrical tape.
    Other than that good to know cheers.
    MKV R32 - no mods..........yet

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    • #3
      So cheap, so simple.

      Comment


      • #4
        Originally posted by *thad* View Post
        Now that you have confirmed it works please remove those horrid scotch locks and solder the wires on! If traveling on rough road it will give you problems in the end. If not at least wrap them in electrical tape.
        Other than that good to know cheers.
        Fair call, thanks. When I was crimping them on I was thinking they were a bit dodgy. My soldering skill suck though, so I will try the taping first and see how I go.

        Originally posted by mikinoz View Post
        So cheap, so simple.
        Yeah, that's what I thought to. I am trying to figure out how the likes of Hayman Reece justify the cost of their towbar + electrics given how cheap and simple this solution is. I got my OEM (made by Best Bars in NZ) towbar off eBay for $400 odd, plus this electircs kit, plus $70 for the expert services of AlexG to help me fit the towbar up - so it was just over $500 all fitted up. Call it $600 at worst. *shrug*
        sigpic
        Tiguan TDI, 6spd Tiptronic Auto
        Black, sunroof, comfort pack, off-road tech, tan leather, park assist & roof bars.
        Avg 7.63L/100km over 189,000kms

        Comment


        • #5
          well done arctra, always great to see someone taking the alternative route and finding a good solution

          cheers
          Tiguan TSI Catalina blue, Manual

          Comment


          • #6
            I have discovered the MY12 wiring is slightly different, there are only 3 wires into the light cluster rather than 4.

            On the right, there is a black/green (indicator), black/purple (brake), brown (earth). While left has a black/white (indicator), yellow/green (brake?) and brown (earth). I wonder if brake and tail share the same wire now.

            Can anyone with access to a wiring schematic or service manual confirm I have identified the correct wiring as per above?
            MY12 Tiguan 132TSI + DSG

            Comment


            • #7
              I'd say you're close to being on the money.

              Stop/tail already shares one single filament globe. So why not share a wire on the output side? The Central Electrics module already steps the voltage up at the globe to differentiate between a tail light and a brake light. You do this using just one wire to the globe. The Central Electrics module already receives an input from the headlight switch, and one from the master cylinder travel sensor (AKA brake light switch).
              '07 Transporter 1.9 TDI
              '01 Beetle 2.0

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              • #8
                Thanks Umai, is the central electrics model housed inside the light cluster?

                Any idea how I can tap this single tail/brake line into a bypass relay to output tail and brake lines separately?
                MY12 Tiguan 132TSI + DSG

                Comment


                • #9
                  Nope. Central Electrics module is above the fuse carrier under the right side of the dash.

                  I would tap into the feed from the headlight switch on the dash that goes to the Central Electrics module to get a tail light signal, and then do the same at the master cylinder travel sensor on the master cylinder for a brake light signal.

                  If you do it this way, you wont or shouldn't have any bulb monitoring issues.

                  For the trouble you'll go to to get it all working, you'll wish you got the genuine kit. Shoot me a PM if you decide to go down that path.
                  '07 Transporter 1.9 TDI
                  '01 Beetle 2.0

                  Comment


                  • #10
                    It looks like the bypass relay I got can take a single brake/tail input and output brake and tail lights separately. Give it a try I guess.
                    Last edited by z1000; 17-05-2012, 01:36 PM.
                    MY12 Tiguan 132TSI + DSG

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                    • #11
                      It turns out the relay I got (7 WAY SMART BYPASS RELAY - TOWBAR, TOWING ELECTRICS MULTIPLEX RELAY | eBay) has no problem outputing tail and brake light individually from a single tail/brake line in a MY12 model. No bulb failure has been detected, so far so good.

                      FYI this relay actually consumes power even when the car is switched off (as it is powered by cig charger in the boot), so I install an line switch in the boot sidewall to enable/disable the relay when required.
                      Last edited by z1000; 19-05-2012, 10:26 AM.
                      MY12 Tiguan 132TSI + DSG

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                      • #12
                        Anyone who uses Scotchlocks deserves all they will get eventually.

                        They are the worst possible way to join wires and the most unsafe. One day you will come back to a smouldering wreck due to one of them defecting and shorting to something.

                        The only worse thing is people who wrap wires around fuse legs.

                        If you cant solder get a friend who can to do it for you and know you will be safe.
                        2021 Kamiq LE 110 , Moon White, BV cameras F & B
                        Mamba Ebike to replace Tiguan

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