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Thread: How to read wiring diagrams - the videos (final version)

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    Ross-Tech Employee Jef's Avatar
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    How to read wiring diagrams - the videos (final version)

    Jef
    Ross Tech Support Team, Alpha Squad
    Auto-Scan, learn it, love it, live it... then check the fuses.

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    good job Jef

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    HI jeff.

    I have Elsawin, which i have slowly learnt, The only part that i cant understand is for some earth circuits it says for example 410. Earth connection 1 in main wiring harness, do you know how to find this earth location,, Where as you know most regular earths on the diagrams such as 605 tells you where it is located,, on top of end of steering column.
    but where is the earth when for example it says earth connection 1.

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    Ross-Tech Employee Jef's Avatar
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    Not sure what you mean by "Earth". I'm guessing a ground. To that end, are you asking about a ground point (threaded stud on the body of the car), or a weld point for a ground? Can you point to an example in the our PDF training material?
    Jef
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    Hi
    Yes earth = Ground for circuit item such as sensor,, i have a fuel gauge, sender, issue and at the dash unit j285 where the ground is at T36/33 on a vw caddy BLS engine code year 2008, the coolant shortage sender, outside air temp sensor also share the same ground number on the diagram,, 410, all the grounds on most of the wiring diagrams are on a threaded stud and the Elsawin shows you where the locations for a particular ground is located,

    Now my problem is for some of the wiring for example the fuel gauge / fuel sender has ground listed a It says exactly Earth connection 1 (sender earth ) in main wiring harness, I have also seen the same for other vw diagrams earth connection 18, 17, etc so they do it quite a lot,

    So i'm trying to find it's location in the harness, it must go to ground somewhere, but it does not show like i said above on a stud for location if you have a look at vw caddy BLS 2008
    1.9turbo diesel with unit injectors BLS, from 2007, click on + Scroll down to page 15 Dash panel insert fuel gauge etc, current flow diagram number 105/15 you will see earth number 410, that is the one i'm talking about, When they say in main wiring harnes, where does it locate ? other wise you cant find the earth (Ground )

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    On some of these "main harness" connections, its actually connected in a group using a "NODE" connector. Unfortunately these have no designation, other than uncovering the loom to find it.

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    Hi Thanks Dubtech.
    A right pain in the arse, Finding them, Uncovering the loom ,that is what i have had to do in the past, some times helps when we have spare looms,, The problem is when you have the dash in place a lot of work to trace, especially if Ground short to plus, or open circuit, I notice on the fuel gauge / sender the 410 earth has links with other items, and they sooner or later have to have a link with the battery negative, as they have continuity with the battery neg terminal as you would suspect,

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    Yeah it will, but what I usually do is find what else is connected in the same "point" it can usually give an estimation of the whereabouts of the node. I done one the other day, with a connection to terminal 15, puddle lights in doors not working, all doors were connected to it, fed from a single pin of j393..... node was below the carpet at the rear of the passenger seat!?

  9. #9
    Ross-Tech Employee Jef's Avatar
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    So the 410 is going to be a weld point in the wiring harness. If I had to hazard a guess, that weld point would be 10" to 20" (254mm to 508mm) from the J285 connector.
    Jef
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    Dub and jeff
    Yes with the fuel gauge sender issue there is a 3 branch Node if you want to call it that, about 12" up from the coolant shortage level sensor, one to oat sensor, one to dash j285 and one to fuel sender, and you can bet somewhere in the loom other sensors on the same earth link 410,, My problem was the front loom had been hacked on the n/s front, ,

    No fuel gauge working, then traced it to the 3 branch i mentioned, but only one wire not 3, so i ran a wire to oat sensor, one to tank sensder, and the gauge should work, put the ignition on nothing, turned it off/back on gauge working, so thought job done,, other jobs to do, then had mot passed,, But when the van was warming up the gauge stopped working,,

    I ran a separate earth to the clocks for the gauge and it worked, turned ignition off/back on and nothing, dtc is saying open circuit or ground to plus, so i think it is shorting somewhere, other wise the earth from battery should of worked, i have battery voltage at the dash j285 , POWER T36/2 ,,30 constant, and T36/ 1,,15 ignition on, and with 30 or 15 at j285 to pin T36/33 battery voltage with earth from battery,,

    If i use the normal earth sometime i have NOTHING, then very low voltage that creaps up if you gently touch the loom at the j285, so you think ok power or earth,Fault break in wire, power to chassis battery voltage all day,, but to std earth erratic, so fresh earth from battery good voltage, the fuel gauge works, turn ignition off, or leave it on, while on, it may then stop working, turn ignition on/ off nothing,, so i think the ground may be ground to plus, as it should be working . Just been checking some of my Obdll stuff and says fuel tank sender if open circuit 510 Ohms, Short circuit 0 ohms,, so must be open circuit, ground or power ? side.
    Last edited by senna1; 06-11-2015 at 05:36 PM.

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