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Thread: Ignition switch wiring

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    Apprentice Hightower's Avatar
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    Default Ignition switch wiring

    In the past my S3 has had a catastrophic wiring overheating and melting incident (not of my doing I hasten to add) which now needs sorting out (read rewire). As part of this I was intending to replace the ignition and associated mechanics with a push button start. However, I do not want a repeat of the melty thing so just wanted to clarify a few things before I get going.

    Brown wire = direct feed from battery +ve
    Brown/red = feed to glow plugs
    White/red = feed to starter solenoid
    White = Everything else (via fuses)

    So, one switch to connect brown to brown/red and brown to white (or should that be two so that glow plugs are switched off independently) and push button for brown to white/red connection. Hey presto, flick switches to arm system and then push button to start . . . . . . .

    Have I got it right, or should I get ready for more smoke and melted plastic?

    Thank you for any help that will put my mind at rest.
    Simon
    1998 Disco Series II TD5 - Not standard
    1972 88" Series 3 - Finished project, back on the road!

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    Default Re: Ignition switch wiring

    . . . .
    Simon
    1998 Disco Series II TD5 - Not standard
    1972 88" Series 3 - Finished project, back on the road!

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    Default Re: Ignition switch wiring

    Well going from the petrol I get

    Brown wire = Permenant live (through fuse)
    White/red = Switched live to starter solenoid
    White = Ignition live via fuses.

    The white/red should only be live in the cranking position. Don't know about the glow plugs I'm afraid, never dealt with diesel series landies!

    If I was re wiring through a set of switches I would also put a masted battery cut off switch in case it did start trying to melt and then you can stop it before any fires start
    Motors : 1980 Series III 109" V8, 2004 Mazda RX-8 (it starts sometimes too)

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    Default Re: Ignition switch wiring

    You'd be better off fitting relays and correct cabling to heavy loads like the glow plugs if not already there to avoid overloads.

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    Default Re: Ignition switch wiring

    Thanks for the repsonses. It looks like I was on the right lines then.

    Will defo have an isolator switch, and everything will go through relays where required.

    Obviously the main query was about how the ignition switch worked. The only thing I haven't figured out is whether the feed to the glow plugs is continuous or not (i.e. does it cut out once the engine is up and running). From the diagrams I have found so far, it is not clear . . . . . .
    Simon
    1998 Disco Series II TD5 - Not standard
    1972 88" Series 3 - Finished project, back on the road!

    Macmillan 4x4 UK Challenge
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    Default Re: Ignition switch wiring

    Don't the glowplugs only preheat the engine before starting?
    1970 Series IIA 2.25 petrol - Many things done, many more to do, even more waiting to leap out of the shadows and break.
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    Default Re: Ignition switch wiring

    Quote Originally Posted by solemnwarning View Post
    Don't the glowplugs only preheat the engine before starting?
    Yes, I believe so, but the ignition switch seems to keep the connection after turning the key to POS3 (i.e. cranking the engine over) and then back to POS2.

    It has been suggested that I have a petrol version of the ignition switch - is this possible?
    Simon
    1998 Disco Series II TD5 - Not standard
    1972 88" Series 3 - Finished project, back on the road!

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    Default Re: Ignition switch wiring

    I belive the diesel ignition switch has seperate starter and preheat positions, so they don't stay on after releasing the key.
    1970 Series IIA 2.25 petrol - Many things done, many more to do, even more waiting to leap out of the shadows and break.
    Useful(?) tools:
    Transmission Calculator
    Speedo Error Calculator
    Tyre Size Decoder

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    Default Re: Ignition switch wiring

    Well, got the new switches and push button start wired in this evening. Connected up the battery, no arcing as I did so was a good sign.

    Flicked the switch for POS1 on the ignition and the lamps on the dash lit up. No smoke or burning smells. Good so far.

    Flicked a switch to send power to the glow plugs, the lamps on the dash dimmed slightly. Still no smoke.

    Pushed the starter button. Engine turned over a few times and then fired up. Loads of smoke, but all out of the exhaust, thankfully.

    Now I know it all works, I've just got to find a suitable place to mount everything. Then finish rewiring the rest of the car . . . . .

    Thanks for your thoughts on this.
    Simon
    1998 Disco Series II TD5 - Not standard
    1972 88" Series 3 - Finished project, back on the road!

    Macmillan 4x4 UK Challenge
    1st Overall - 2014, 2013, 2011, 2010, 2009, 2008, 2006, 2005
    2nd Overall - 2012
    3rd Overall - 2007

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