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Thread: 24 Volt Mystery

  1. #1
    Join Date
    Feb 2020
    Location
    NZ
    Posts
    1

    24 Volt Mystery

    So, I have just purchased a 1985 110. 2.5 NA diesel.
    Its ex Singapore military and has the 24v wiring.
    Everything in the vehicle is 24V. 2 batteries in series and huge ass alternator...

    The vehicle wasn't running when I got it
    I went through everything and found that all the glow plugs were dead.
    Installed new glow plugs and it fired up straight away after a 15 sec glow.
    Went to start it the next day and it wouldnt go.
    Pulled the glow plugs out and found no4. and no.2 had melted tips and no.3 and no.1 while not melted are very dead.

    System has a relay on the bulkhead. That seems to check out ok.
    Comes on when the key is in the glow position and goes off when released.
    The feed to the plugs from the relay is 24V according to the meter.

    Next to the relay is a small ballast resistor with 1 very thin wire attached to each end . Not sure why its there or what its supposed to do.

    The glow plugs are wired in series.

    The new glow plugs have 11V stamped on them. Checked the old plugs that came with the car and they are also 11V. Can't blame the parts guy for this one!

    My question then is...Should I have 24V glow plugs? OR is 11V correct and something else is going on?
    If I do need 24V plugs where can I find some that do not have an insane price tag attached to them?
    I'm hoping someone here can shed some light on this as the mention of 24V makes parts people go crosseyed here in NZ.

    Cheers

  2. #2
    Join Date
    Aug 2006
    Location
    Melbourn(ish)
    Posts
    25,933
    there should be a center tap wire that feeds that relay giving only 12V to the glow plugs, the resistor is most likely just a voltage dropper to let a 12V relay function to turn this on.

    get some more 11V glow plugs, their resistance should be in the range of .75 ohm each with a reading in the range of .1-.2 ohm for all 4 in parallel.

    What you want to do is grab a snarking great resistor (heater element wire works well) and wire it in series with the 11v glow plugs and the feed the lot 24v.

    Smart people wire the resistor in in the inlet manifold.

    you could also get 6v glow plugs and wire them in series in the same way as the series diesel uses 3v glow plugs
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    TDI D1(parting/ed)
    Tdi autoManual d1 (Kept it for the girlfriend)
    Archaeopteryx 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.

  3. #3
    Join Date
    Aug 2006
    Location
    Melbourn(ish)
    Posts
    25,933
    you can also...

    wire them in 2 banks of 2 in a series parallel configuration or...

    get a 24V 30a PWM and wire that up to drive the glow plugs at 11V (or use a 24V1a PWM to drive 4 mosfets through 4 current limiting resistors so the mosfet it delivering the required current to the plugs)

    OR hook each glow plug up via a 70w headlight bulb (in reality you could probably just do one, once once cylinders hitting the rest catch on pretty quick)

    OR

    make a dedicated 12V circuit for the glow plugs using a second battery and have it charge via a 24-12V DC-DC at about 8A controlled through a VSR (assuming the DC-DC doesnt have one built into it) connected to the ignition and oil pressure switch (so it wont turn on till the engine is running) This also has the advantage of giving you a non critical 12V power supply for cig sockets and the like that dont like 24v for accessories

    or

    you could fit a 24V inlet heater

    or you could fit a 24v diesel fired webasto that also preheats the block

    or you could just move to QLD/NT where the glow plugs only really serve to keep the compression and combustion gasses in.
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    TDI D1(parting/ed)
    Tdi autoManual d1 (Kept it for the girlfriend)
    Archaeopteryx 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.

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