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Wiring into ignition help

Discussion in 'Technical and Troubleshooting Torque' started by ashrose, Jul 17, 2015.

  1. ok guys im wondering if someone could give me some simple instructions on how to wire extra lights
    so they are only useable when i turn the ignition on.

    ok so here's what the story is.
    i just got some LED 6" light bars and i what to hook them up.
    problem is i have a neighbour who has a kid that gets into everything and i dont want to go out in the morning to find she has turned my lights on and flattened my battery (same at work)

    i have a wiring loom (with 40amp fuse and relay) that will go straight in from the battery to its own switch.
    i want to find a way to wire the switch so it only goes live when i turn the ignition on.

    the switch (enclosed wires) has blue/ black/ white wires coming from it to a little connecting box that then connects to the second arm of the loom (to the relay) and the same colors go into the relay.
    at the relay the blue wire connects by its self, the black wire connects to the relay with 2 other black wires (i assume thats the ground) and the white goes into the relay with a red wire (red goes to fuse then battery).

    the second arm of the loom has a red and black wire ( pos/neg ) that go to the lights.

    like i said if someone can give me some easy to follow instructions on how and or where to wire the switch up (if i can) that would be awesome.

    thanks for taking the time to read and respond if you do.

    ps. ive looked all over the net and couldnt find what i needed to do.

  2. Hi Ashley,
    This guy does a pretty good job of explaining the task.
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  3. That video = Butchery.. fcuk me!

    I don't like scotchlocks, Positaps or crimp connectors.

    Use a fcuking relay to switch!!!
    • Agree Agree x 3
  4. Because there are 3 wires coming from the switch, I assume it has a light in it.(that's what the black return wire is for) The white is power feed, and the blue is relay trigger.

    Just cut the white wire between the switch and the relay. hook the white wire from the switch to any ignition on wire in your bike loom.
    • Like Like x 1
  5. Scotchlocks are for quick emergency fix only, not permanent, and can cause damage.
    Soldering is not a good solution at connectors, it weakens and breaks. Soldering should really only be done in a supported wire run/loom.
    Crimp are the only way to go. OEM are all crimp. You have to have the right connector and tool though. Scotchlocks etc, are a problem because not only can they corrode, or cause a high R joint, they can also cut strands in the wire,(less current carrying ability) causing a higher resistance in the wire, which can cause heating and melting.
    In this case though, the relay and switch light is only using probably somewhere around 100 milli amps or so.
  6. #6 Al_Cam, Jul 17, 2015
    Last edited: Jul 17, 2015
    Can't quiet work out your description of what you have (not enough coffee), but this might help. If it's a normal automotive relay, they usually have a standard numbering system for the terminals. Sometimes moulded into the base near the pins or printed on the top, like this:
    Relay standard.


    Relay micro.

    If you don't want the lights to be switched on when the bikes unattended then you need to take the power to energise the relay from the "run" wire. When you switch the key to the run position and the dash lights up &c... you've energised a relay which then powers up some of the stuff. Move it to start and release the key it springs back to Run. Typically the wire that is on the output side of the relay is Brown. So Red is often Live or permanently powered and Brown is only live when the key is in Run. Maybe. Note that a relay coil or contacts don't have polarity so 85 can swap with 86 & 30 can swap with 87. Maybe labouring the point but the with a relay anything around the coil is low power & can use light wires and the contact side is high power, so you want heavy wires & a fuse too. Fuse also if you are wiring straight to the battery so you don't turn a stuff up into a fire under your seat.

    What I've drawn is a "Common Earth" system. Some lighting systems can have a common positive, where the globe is permanently wired to supply and the relay switches the other side to ground. Something to watch if you are picking up power or earth from around the factory lights.

    Wirirng up lights.

    Oh and Scotchlocks have their place, but nowhere near anything of mine. If I can't find anything else I might disassenble the connector on a relay base and solder a light wire to the back of the factory terminal for the Run wire - Light gauge for the coil. If the factory wire isn't too big and there's room in the socket, maybe crimp on a new terminal with the original and my new tap wire. Wiring to the battery I usually run a new wire with eye terminal and add to the existing battery terminal screw/bolt.

    What I've left out is the LED light regulator/ballast. LEDs don't run at 12V, but less than 2V. So there may be a separate box between the LED and it's power. Or may be built into the LED light itself.

    • Like Like x 1
  7. Just realized, 40 amp and lightbar. Hope it's going on the car and not the bike. :)

    From your description, I drew up the following. Just cut the white wire close to the relay socket, and hook this wire to an ignition switched wire. The little indicator LED and the relay will pull bugger all current.


    Al_CamAl_Cam , some relays are polarity sensitive. In this case it won't matter because it's a prewired installation. Some have reverse biased diodes across the coil for back EMF quenching. Sometimes called freewheeling diodes. Usually only for spike sensitive circuits, but you don't want to hook these up backwards.
  8. Ah yes correct. My bad.

  9. thanks, thats pretty much what im after.
    yeah its for the bike. it was a loom pre-made (you think 40am fuse is too much).
    i want to hook up one or two 6" light bars (18watt each) for country night riding if i have to do it.

    what sort of ignition source should i look for ( i have no idea) can i take it from the ignition switch (thing you stick the key in)

    anyway thank you to you all
  10. Yes, 2 x 18watt = 36watt.
    36watt/12 volt = 3 amps.

    You generally allow a bit extra to allow for derating in hot conditions. The fuse is to protect the wiring not the lights. A 5 amp fuse is sufficient.

    You may not get easy access to the key switch. A circuit that is live when the bike is on. commonly the rear running light is a point you can get in to the circuit of. This is a ssuming it is a bike where you can't turn off the lights.
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  11. thanks cjvfr (chris)
    hopefully i can get it done this weekend and i'll post some pics

  12. Al_CamAl_Cam

    What schematic software are you using for you drawings?
    I have been using CircuitMaker, but it's long out of date now, still good for basic digital sim though.

    I am just checking out Fritzing, for drawing only with no sim, seems o/k so far, and can easilly colour wires.

    • Informative Informative x 1
  13. ValfarValfar Umm avoids eye contact. I just cyber-slacked at work over lunch and did that on ms-powerpoint. Leased PCs and rolled-over recently haven't got round to reinstalling non SOE stuff. Thanks for the suggestion though. I've been using paper & pencil been meaning to hunt something up.

    Haven't worked in design for some years. We just buy boxes from CISCO &c... Most complicated design I've done the last while was a PWM soft start low voltage drop-out for the bike's halogens headlights using a boot-strap high side driven P channel MOSFET. And yes I used a ultra high speed Schottky for the switching spikes, 'cause that's what I had :). Made lovely flashing headlights with a 3 sec duty cycle. "Huh? Oh that's right, hysteresis". Amusing but not much use for riding at night. Gave up and brought LED H4 globes.
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  14. Yep, hysteresis, switching levels and time, makes for some interesting results :)

    The last major project I did was a fully simulated and then built set of Drag lights.
    Stage and guard beams, finish beams etc. All using logic IC's, no micro controller, just pure logic,timers and counters. Has win lockouts, staging lockouts etc. I originally built the system with relays controlling the Xmas tree lights, but this caused too many spikes, false triggers, I couldn't get rid of them even with diodes and filters on the relay coils. Changed over to solid state relays (SCR, thyristors) and it worked perfect. If I had to do it again, I would use a micro controller, lot less wiring and components.
    The system is for the V8 dirt dragger guys. Bikes with supercharged nitrous V8's or V6's, centrifugal lock up clutches, and massive paddles. I wire up the computers for these guys as well. Mainly they use Alltronics.

    I used PowerPoint a lot for drawing circuits, just drew my symbols and saved them in a library folder. I still reckon PPoint is a good prog for quick stuff. I use it a lot.The one I drew above was symbols from circuit maker, and I drew the lines and text in MS Paint:)
  15. Cool.

    I sometimes wish I could still solve my problems at work (mostly human) with the tools I used in earlier, happier days: a CRO probe & a Soldering iron.
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  16. 1 x18w light is only 1.5 amps @ 12v so you don't really need a relay , you could get away with running it straight from the headlight so that they both come on together. The headlight circuit on ur bike including your handlebar switch is rated for more than it ever uses normally so there's plenty of room for an extra 1.5 amp. Even 3amp would be ok but on the other hand relays are a good learning experience and won't hurt anything but are a bit overkill for a basic led light. I actually enjoy wiring relays I've just replaced my main starter relay with a 100amp solid state one , was it needed? Nope, but it will never fail at least.
  17. Yep, relays are fun. I actually built a relay computer once, using 100's of relays.
    Way too much time involved. I just use a sim to do the same thing now. You can wire relays to perform most basic Boolean logic functions.

    The OP had the relay loom already, so makes sense to use it.

    Can you think why it would be a good idea to isolate the LED bar from the main headlight supply? With a 5 amp protection fuse on the LED's, add the 5 or so amps from the H/Light, and in the event of a short on the LED's, you will pull at least 10 amps before the 5 amp fuse blows. This will compromise or blow the main H/Light fuse.
    Also, most modern bikes run very close to the limit with current carrying capability of the wires and switches.
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