Headlight Cut UNTIL start

Discussion in 'Custom Mods' started by DEcosse, Jun 8, 2011.

  1. DEcosse

    DEcosse .020 Over

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    You guys may be interested in the Headlight Cut Modification I designed

    This is for bikes without a headlight control switch - this fairly simple mod will keep the lights off completely until after it is started.

    Currently, when the ignition is initially turned on, the headlights come on immediately.
    Triumph incorporated a 'cut while starting' feature however, so that the lights go off while the starter motor is engaged.
    But here is a fairly simple modification that takes it a step further
    - by adding in one more relay, the lights will remain off completely until after the starter is pressed and released.
    (note that lights will not come on until the button is actually released, not when initially pressed)
    This is actually a great feature for those of you using TuneECU - there is no need to pull any fuses when this mod has been installed.
    Total cost will be less than $10
    You need one 12V relay (20A minimum rating), Three* diodes and some wire - that is it!
    * If you use a relay that already utilizes suppression resistor or diode, you will only need two diodes

    How it works:
    When ignition is first turned on, the new relay will be 'off' inhibiting power to the OEM starter relay.
    When the starter button is pressed, the new relay will energize along with the OEM starter relay, completing the circuit through both relays to the starter solenoid.
    When the starter button is released, the 'new' relay will remain on however - it will self-latch because of the connection from its output (87) through the diode (D2) back to the input (86).
    The diode (D1) in the starter line prevents the current from flowing back to the starter relay, otherwise it would keep the starter relay energized.
    i.e. this diode allows the starter signal to flow to the new relay, but not from the new relay to flow back to the starter signal.
    And when the starter button is released, the OEM starter relay de-energizes and switches power from the now-latched new relay, to the headlights.
    The new relay will remain latched on as long as ignition switch is on - will reset when ignition turned off.
    The diode (D3)* is added across the coil for turn-off spike suppression (good practice when adding relays for ANY purpose)
    *D3 not required if using a relay with internal suppression (diode or resistor) already
    This will make for minimal drain from battery when you first turn on ignition. Also useful for those maintenance activities (like TuneECU for example) where you might want to have the ignition on, but not have lights on.

    Note that you can omit the Suppression Diode (D3) between 85 & 86 completely if you use a relay that has a diode (or resistor) already installed.
    The suppression diode is not integral to the actual circuit mod, but good practice when installing any relay in any application (often omitted!)

    Here is step by step process on how to wire the original (above) up
    (make the appropriate changes if doing the HID circuit at the bottom)
    All you need is a relay, socket (ideally) and three diodes.
    I like to use the compact Panasonic relays - good for 20A and much smaller/neater form factor than std. Automotive style relays.
    You can also use the Omron style relays used as OEM - also compact (and OEM has built in resistor so can skip D3)
    But a Generic 4 terminal automotive relay may also be used. (or even 5 terminal - just ignore the 87a centre terminal which will not be used)
    Just be sure to identify the terminals appropriately for whichever relay you end up using.
    I would advise a 20A mimimum rated device

    For diodes (for example)
    In US - from Radio Shack Model: 1N5399-S RS Part #: 276-1114 - 1N5399-S Silicon Diodes (3-Pack) - RadioShack.com ($2.19 for pack of 3)
    In UK - from Maplins - 1N5404 - Part # QL84F (£0.29 ea) or 1N4007 Part # QL79L (£0.24 ea) Rectifier Diode : Diodes : Maplin

    Step 1.
    Prep first relay terminal by joining the three* diode cathodes (ends with the white stripe) together and crimping/soldering.
    This terminal is for the 86 location in the relay socket
    * Note that if your relay has built-in suppression diode or resistor, you may omit D3 and only require two diodes (see step 5)


    Step 2.
    Crimp/solder the Anode of ONE of the three Diodes and a 14 ga wire together to another Terminal.
    This terminal is for the 87 location of the relay socket.
    (This wire will be the Output wire ultimately connecting to the OEM start Relay input)


    Step 3.
    Connect the Anode of another of the three diodes to an 18 ga wire.
    (This wire will ultimately connect to the White/Red starter signal wire)


    Step 4.
    Heatshrink over the diode and wire from step 3


    Step 5.
    Crimp/solder the Anode of the remaining Diode along with an 18 ga wire together to another Terminal.
    This terminal will be for the 85 location of the Relay Socket
    (This wire will be the Ground wire for the relay coil ultimately connecting to a common ground reference)
    * If a relay utilizing built-in suppression is used, connect the ground wire directly to the termnal without the additional D3 diode

    Step 6.
    Install the three assembled terminals into the 87, 86 & 85 locations of the relay socket.
    Of course plan ahead for whatever relay/socket you are using to ensure the correct locations are selcted.

    Step 7.
    It is critical that the two exposed Anodes do not touch!
    These should be physically isolated from each other and coated with something like liquid tape or heatshrink over the idividual components.


    Step 8.
    Final step can be to tidy with heatshrink sleeve.


    1. Remove the Blue/Yellow wire/Terminal from the input to the OEM Starter Relay and insert this wire/terminal into the remaining open location (30) in the new relay socket
    2. Attach a Terminal to the Blue Wire and insert this in the OEM Starter Relay socket location from which Blue/Yellow was removed in step 1
    3. Attach the starter wire from the new relay to the white/red wire of the OEM Starter relay (if your relay has two white/red wires use the one on the input side i.e. from the start switch)
    4. Connect the black wire to a ground circuit wire (any) or battery negative.

    1. Test without starting:
    Turn on Ignition, lights should remain OFF;
    Press 'Start' button (NO clutch!) and hold - lights should still remain OFF;
    Release 'Start' button - lights should come ON.
    Turn off Ignition - Lights should go OFF.
    Turn Ignition back on - Lights should remain OFF (until 'Start' pressed/released again).
    This procedure (Start button/no clutch) may be used at any time if you wish to turn on lights without starting.
    2. Test with starting:
    As per Test 1, but this time pull clutch lever which will also start engine.*
    Lights should remain OFF BEFORE AND DURING start, then come ON when button is released.
    If you stop 'crank' before engine fires, lights will actually come ON when button is released
    - however should go OFF again when 'Start' pressed again (as per pre-mod condition) and back ON when 'Start' released.

    Alternative scheme for HIDs:

    With the original scheme above, there may be a very small instant as the relays first switch states where the lights comes on for a few milliseconds - this is just due to the finite time it takes for the electromechanical relays to change over.
    This is really inconsequential when operating with incandescent bulbs.
    However if using HIDs, it would be preferred not to have even this minimal power duration to them
    This modified version will work for that situation and will not power the HIDs until after the start process is completed.
    It can also be used for non-HID application if desired, but the added complexity (albeit minimal) of the capacitor is not necessary for incandescents.
    Note that this one is AFTER the start relay, vs the original which is before.
    Because of that, the capacitor must be added to ensure that the relay remains on momentarily after the start button is released, to ensure that the relay will latch.
    Also note that this revision may also be used for non-HID if preferred - however the downside is the added complexity (albeit minimal with the capacitor) but also that the pre-start turn-on (as explained in Test 1 above) will not work with this rev - the clutch lever must be pulled and the start relay energized (i.e. powering the starter) in order to complete the cycle to turn on the lights.


    *small caveat - neither has been specifically tested on a Rocket - however has been proven on other Triumph models that utilize virtually identical scheme.
    69birdflu, brewmaster, tsmith and 3 others like this.
  2. liquidsmile

    liquidsmile .020 Over

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    Detailed write up with pics. Mods make this a sticky. All in favor say I.

    sunsettt likes this.
  3. tsmith

    tsmith Standard Bore

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    North Dakota
    great idea. will do mine soon.
  4. bagman

    bagman .020 Over

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    already ordered the stuff for this one. 2nd sticky!!
  5. DEcosse

    DEcosse .020 Over

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    I think you'll enjoy this mod - be sure to report back when you have it installed. :D
  6. JoseyR3Wales

    JoseyR3Wales Constitutionalist

    United States
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    2006 Rocket III Classic and 2011 Thunderbird Storm
    Very nice work
  7. atomsplitter

    atomsplitter .060 Over

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    Scranton, KS
    Eastern Beaver's H-4 relay kit with Lo-Beam Cutout does the same thing. It adds a toggle switch to turn the lights off. That means you can start and run the bike with low beams off (sort of like pre-1974). It's a simpler install too, but to each his (or her) own.

    I used the right hand side frame cover to mount the toggle switch (water-proof) so I can flip a switch to prevent the lights coming on when I turn the ignition on.:cool:
  8. albertaduke

    albertaduke Turbocharged

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    in calgary in the cold most of the time
    2006 standard

    that is exactly what I did with mine and it is just perfect I placed the switch right behind the left side panel fact I even took a picture and saboteur with sharp eyes saw it on a picture I posted some time ago
  9. HellFire

    HellFire Legend

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    Yes, since the Easter Beaver Relay Kit is an absolute MUST anyway ... you might as well order it with the low beam cut off and be done with it.

    Even those with single headlight Touring models benefit from the increased illumination and brighter white headlights though their ignition switches might not have the terrible load on them duals do.
  10. DEcosse

    DEcosse .020 Over

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    I agree headlight power relay kit is an extremely positive attribute - have them on all my bikes and am huge advocate for that. But there is no reason this cannot be used in conjuntion with that. It is to control the headlight-on function, not the power delivery, which is separate mod regardless of whether you add a discrete switch or choose this method. So let's not confuse the issue of improving headlight function through a power relay kit, vs this.
    Maybe some riders don't even ride at night & don't care about the actual headlight performance - this is still a low cost solution to keeping the lights off prior to starting.

    The benefits in my view vs the 'switch' option in the EB kit
    1) It's automated
    2) No additional switch to purchase/mount
    3) Costs less (significantly with regards to the switch)
    4) Effective regardless of whether a power relay kit is installed - or not i.e. you HAVE to install a relay kit in order to install a switch
    5) Simple, hidden installation.
    6) You can't forget to turn your lights on

    Bottom line is, to each his own:
    There is nothing wrong with adding a switch if that is your preference - personally I don't like to add additional switches, especially on a naked bike, if there is a way around them. To that end I designed my RFID system to utilize the clutch-switch as a trigger, just as with this system, it utlizes an existing OEM control, the start switch.

    One downside of a discrete switch:
    - I have a manual switch on my Daytona (sourced from an early model before they nixed them - OEM intergated into left bar switch assembly). I can tell you honestly that I invariably never turn it off when I get home; that means when I go to start bike, turn on ignition and lights come on & of course I realize & turn them off. And I can't tell you how many times have set off in daytime and my riding partner signals to me that my lights are not on, having forgotten! - often after quite a ways out if I am the front rider. That is my honest personal experience, not some added fluff to convince you to do this.
    Even on that bike, I have retained the switch but added this mod anyway.

    But I'm not here to tell you 'this is better than that' - I'm just offering an a cost-effective automated alternative for those who might enjoy it. Not trying to sell anyone anything - it's all there if you decide to do it.
    brewmaster, rocketpockets05 and bertb like this.
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Triumph Rocket III