headlight cutoff switch for cranking

Hello, I have a 2007 Yamaha V Star 1100 Silverado.  I want to install a master on/off switch for my headlight only so I hav more power while cranking.  I accidentally dscovered the benefit when my low beam filament burnt out and I was able to crank much easier in the mornings by having switch to low beam with no power draw on battery.  The down side is that I have high beam only right now or nothing (low beam setting).  I have the replacement bulb ready but I want to install a master switch first.  I am thinking I need to interrupt the power before it goes to my existing handle bar Hi/Low switch in order to do this.  I have read some info about needing a relay and a switch, does the relay make this process easier/safer?  I don't really understand relays but I plan to read the site and learn.  All of my experience is with house wiring or direct wiring car accessories.  I'm a little lost.

I would appreciate any and all assistance.  Very nice website, glad I joined.

bigdog3162

You could automate it...
That involves connecting the relay's coil s that #86 goes to IGN +12V and #85 to the starter motor switch +12V (whether at the motor, its solenoid, or maybe the start-switch output).
When the starter is cranking, both coil sides are +12V - hence 0V across the coil and the relay is de-energised.   When not cranking, coil #85 grounds thru the starter or solenoid windings and the relay is energised.

The NO (Normally Open) relay contacts #30 & #87 - which are closed when not cranking if wired as above - are inserted in-line with the beam's +12V supply.

If the beams already have relays, then just connect their relay's coil ground(s) to the starter (etc) as above.
If not, I'd be tempted to fit relays for both filaments for the usual reasons (ie, better lighting; less strain on switches and harness wiring) and use an auto-resetting circuit breaker to each relay from the battery.

Otherwise a single "master cut out" relay is inserted in the supply to the beam switch as above, but that relay is energised whenever IGN is on.


The master cut-out could also be done with an SPDT relay whereby the NC (Normally Closed) contacts #30 & #87a are used instead by wiring the coil between the starter and GND instead of +12V. (By convention, #86 should be the more +ve, hence to the starter and #85 to GND.)
The relay thus energises during cranking and opens the #30-#87a circuit thus interrupting the power to the beam circuit.

However to avoid lights extinguishing if the un-energised NC 30-87a contacts bounce, I'd suggest the "energised ON" #30-#87 SPST relay version.
But for extra redundancy (one self-resetting circuit breaker and one relay for EACH beam), I'd suggest my aforementioned "tempted" method.

Then again, if lights are always on with IGN, then the "always on" single master relay option isn't too bad.


If you have a different switching arrangement - eg, GND switching of lights or starter solenoid - then the above may need modification, but the method remains the same - ie, when NOT cranking, the starter windings are used to GND the coil- (or provide +12V to a grounded relay coil if the starter is "hot" and cranks with a grounding circuit).


I hope I haven't complicated things with to all the options...

Wow..  That sounds really complicated to a novice like myself.  I just ordered a Kuryakyn universal handlebar switch and harness with relay and fuse for after market motorcycle lighting applications.  I plan to use it as a master switch to power the existing headlight high / low switch directly from the battery and bypass the cycle's main power harness.  I think that will be easier for me.  Thanks for the reply but your suggestion is beyond my expertise or comfort zone.

bigdog3162