How to: Add a Headlight Cutoff Relay.

[Quimrider]

You may have noticed most other motorcycles have a relay that turns off the headlight when the starter button is pushed. Unhappy that my GZ did not have this function, I decided to take it one step further and have the headlight off when the kick stand is down. I will also tell you how to add one if you just want it to turn the headlight off when you press the start button.

Materials needed.
-1 SPST (Single Pole Single Throw) automotive relay
-1 diode
-electrical tape and/or heat shrink tubing.
-16 or 18 gauge wire no more than a couple feet.
-3 blue female crimp on ends.
NOTE: Both relay and diode are readily available at Radio Shack. There is nothing special about the diode don't worry about trying to find a specific one. This one from parts express would work too.

Tools needed:
-Wire stripper / crimper.
-Soldering Iron and solder.
-#2 Philips.
-Lighter if you use heat shrink tubing.

Not necessary but it helps to understand what a relay is and how it works. If you are familiar with relays skip this section. A relay is an electrically actuated switch. This page has some good basic info. A couple of terms to be familiar with are "N/O" (normally open), "N/C" (normally closed) and "Common" See images below. The common and the N/C terminals are electrically connected when the coil IS NOT energized. The common and N/O terminals are electrically connected when the coil IS energized.


Operational summary:
We will be using the common and N/O contacts to switch the head light. The kick stand switch provides a ground when the kick stand is down. The diode will be used to prevent current from feeding back into the kickstand relay circuit. The power for the relay will come from the headlight circuit.


Step 1. Prep relay wires with female terminals as shown. These will be referred to as "relay wires" in the steps below.


Step 2. Remove your seat to get at the fuse area. Gently rock the fuse box back and forth while pulling forward. There are just two rubber grommets holding the fuse box to it's mount. See circled mount below.



Step 3. Carefully peel back the sheathing of the wire bundle coming out of the fuse box. We will be using two wires from here. You will be re-using this wrap so don't destroy it.



Step 4. Locate the Green and the White wires to be cut. DO NOT cut any wires yet we are just locating them for now. There will be two White wires. One supplies the +12V for the head light and the other goes to the headlight. Pull out the "Headlight LO" fuse. Turn the key to "On" and use a multimeter to test for voltage on both white wires. The white wire that has no voltage on it is the one we want. Mark this wire so you know which one it is.


Step 5. REMOVE THE KEY from the ignition so there is no power. If it makes you feel better you can unhook the battery but this is not necessary.

Step 6. Determine the proper orientation of the diode. It is very important which direction the diode faces. The green wire will be cut and each end soldered to the diode. As shown below the one end of the diode has a white band which is oriented away from the fuse box.


Step 7. Install the diode and ground wire for the coil. Cut the green wire. Trim the leads on the diode. Solder the white band side of the diode to the green wire (that goes into the wire bundle) and one of your relay wires with 1 female terminal. Solder the non-white band side of the diode to the green wire coming from the fuse box. If you are using heat shrink tube don't forget to put the heat shrink tube on before soldering! See image after step 9.

Step 8. Solder relay wires to the marked white wire. Cut the white wire that you marked in step 4. Solder the relay wire with two female terminals to the white wire coming from the fuse box (fused headlight power source). Solder the remaining relay wire to the white wire going into the wire bundle(wire to headlight). After soldering and heat shrink wrapping the wires you should have something like the image below.

Step 9. The relay wires connect as follows:
-The wire with the two female terminals connect to 30 and 85 on the relay. The relay wire connected to the green connects to terminal 86 on the relay(I marked this black with a sharpie so I knew it was the coil ground). The remaining relay wire connects to 87 on the relay. If your relay has an 87a this terminal is not used and should be insulated to prevent the possibility of something shorting against it. You should have something like the picture below after completing steps 7, 8, and 9.


Step 10. Reapply the wrap around the wire bundle. I used a zip tie here and there to keep things neat.


Step 11. Find a sutible place to install the relay. I chose the lazy man's way of simply zip tying it to the side stand relay. Carefully wiggle the fuse bock back on it's bracket. Be careful those rubber grommets have a tendency to want to roll up.


Step 12. Wrap up. Put key in ignition turn to on and test for functionality. Put everything back together and you are done!


If you wanted to use a relay to just cut out the headlight when you press the starter button you will need a relay with a N/C contact (87a) Such as this relay from parts express The radio shack by me did not have any of these.

The steps are almost the same as above except you leave the green wire alone, do not use a diode, and have 4 relay wires with ONE female terminal each. Solder a relay wire with ONE female terminal to each end of the white wire you cut in step 8. Attach the relay wires from the white wire to terminals 30 and 87a(it does not matter which one is connected to 30 and which one is connected to 87a) on the relay. Connect a wire from the - battery terminal to terminal 85 on the relay(relay coil ground). One of the wires connected to the screw terminals does not have +12V. I believe it should be the black wire. I forgot to test this when I had things apart. Connect whichever wire does not have +12V to terminal 86(relay coil +12v).


When you press the start button the coil will be energized as the same time the starter is energized. Energizing the coil switched the headlight off. Alternately you could use the the yellow wire with black stripe as the +12v for the relay coil.

If for some reason you would need the head light on with the kick stand down, The HI beam is not affected by this mod.

Fire away with any questions :rawk:

[alanmcorcoran]

Hey Quim,

I will probably never do this mod (too lazy - but I like the idea!), but I want to commend you on the excellent step by step instructions. Thanks for taking the time to lay this out in such simple detail that even a mechanical idiot like me thinks he has a shot at doing it himself...

[Easy Rider]

Originally Posted by alanmcorcoran

Hey Quim,

I will probably never do this mod (too lazy - but I like the idea!),

but I want to commend you on the excellent step by step instructions.

Thanks for taking the time to lay this out in such simple detail that even a mechanical idiot like me thinks he has a shot at doing it himself...

:plus1:

:plus1:

AND

:plus1:

Good job. 40 years ago, I would have loved to tackle something like that. Now-a-days, not so much!

[trykemike]

Hey Quim .

Brilliant write-up.

Concise and step by step.

Thanks