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spot lights

Discussion in 'Fuel System & Electrics' started by chris taylor, Jun 9, 2018.

  1. Mordred

    Mordred Super Moderator Staff Member

    Penna, Hobart
    Just to throw a spanner in the works, as Cbus said the fuse is there to protect the cable from getting too hot and he is quite correct but there are other factors that also need to be considered. The main one is resistance in ohms per metre which is dependant on the cable size, bigger has a lower resistance. This gives a voltage drop which will increase with length and with small cables and 12v (or worse with 6v) you will lose a considerable proportion of the 12v you have from the battery.

    The cable may be rated for 16 amp for example but you run from the battery to the front of the car and you will lose a lot over the available voltage. Over 5m a 1,5 mm cable will lose 1.83 V at 16 amps. Increase to a 4mm cable and you lose only .6V, so brighter lights.

    The feed cable to the Fuse box is around 6mm I believe and already has a reasonable load on it with the standard accessories. Run a bigger stranded cable to with a fuse near the battery if you want to feed the spot lights and use a wire from the standard high beams to operate the relay for the new lights. Still only rate the fuse at 16 amps then you can use smaller cable from the relay to the lights as it is a shorter run, but the fuse will still protect the cable.

    There is likely lots of calculators around but this was the first I found. works with 6 -12- 24 volt and also has some other good info.



  2. chris taylor

    chris taylor Well-Known Member

    adelaide sth aust
  3. chris taylor

    chris taylor Well-Known Member

    adelaide sth aust
    Made a start on the rewiring of the fog lights {or spots }The heaviest cable i could get was 4mm which is has a rating of 25 amp so the guy said ,so thats suitable for what i want to do, also fitted a 15 amp in line fuse ,now have threaded the cable through to the cab via the inside of the cupboards , Tomorrow will take out light switch and clean the terminals then see where the existing wiring goes to, as in which hot wire it is fixed to, then all being ok hopefully i may be able to cut it and re attach it to new wire from the battery:rolleyes: and then have every thing work with out having to alter to much, well thats the theory.:D
    Mordred and David H like this.
  4. cbus

    cbus Well-Known Member

    sunshine coast
    Mordred likes this.
  5. syncro

    syncro Well-Known Member

    Southern Highlands
    That is an Australia only sizing called bogan standards. It is really dumb and doesn't mean anything. The conductor size is what matters.

    Spot lights need to be wired to only work through high beam. Those inline fuseholders usually are only rated at 10 amps.

    The spot lights need to be wired through relays.

    Relay connections.
    Large red cable to + from battery or battery side of fusholder. Terminal 30
    Small brown cable to earth Terminal 85
    Large white cables to lights through fuseholders. Terminal 87
    Small white cable to existing high beam fuse. Terminal 86

    Mordred and chris taylor like this.

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