So, after some head scratching on a Red Cat’s tenere headlight, I figured I’d post a short explanation of what exactly goes on with this electrical critter.
Usual disclaimer….If you happen to read my written drivel, and decide to follow it, and then break it and/or blow it up, don’t blame me 🙂
First off, If you don’t have the Yamaha (aka: Y) repair manual (aka: M), get one, it can be had gratis somewhere on the world-wide web, and is damn handy.
The original design of the Y headlight has four wires going to it, through a male/female connector on the battery side of the bike. Please reference the picture below. For simplicity sake, I will write out the wire names as they are shown on the diagram.
The L/R wire goes to the G wire. This is the 12V for your marker lights. It powers up with your ignition (aka: Ig), and stays on till the Ig is turned off.
The L/B wire goes to the L wire. This is the 12V for your low beam lights. It powers on only when the bike is actually turned on (1-2 second delay)
The Y wire goes to the R wire. This is the 12V for you shutter relays. It powers on only through the high beam switch.
The last wire is the B, which is the common ground shared by all loads (two markers, two beams, two relays)
I’m a electrician by trade, and I do not pretend to have it all sorted out. But I will explain the issue as best as I understand it in my squishy brain.
I will explain the issue with a simple light bulb. For a circuit to work, you need a source voltage (we’ll use 12 V DC), but you also need a return path. Basically a loop. If any of these two wires become compromised in any way (excessive current which creates heat, moisture, a bad return path etc..) the headlight, and wires will not work as intended.
What happens with the ST set up, is that Yamaha under estimated the draw the over all headlight will have on these 4 wires. The stock bulbs stress the headlight wire, by using it, and the insulation that protects it to the extreme. This wire heats up (usually at the headlight connectors, or at the 4 pin connector). This becomes worse still, when the marker lights, and the shutter relay (on high beam only) share the headlights return path (ground wire).
Forum muppets like myself that did not know about the problem dig a deeper hole by replacing the stock bulbs with sweet ass 55W jobbies (sylvania silverstar comes to mind). The stock wiring barely supports the stock bulb, then a higher draw is requested from the wires. This will end in tears.
I only found out that my connectors were burned to a crisp, when I installed my dual HID kit, moar here: https://thetenerist.wordpress.com/2013/01/08/hid-install-on-the-vfr/
The easiest fix for this issue, is to isolate the headlight lead, and ground, by running a dedicated 12V feed (through a relay mind you), and a ground directly to the headlight harness/HID.
This will avoid any burn wires, breakdowns etc.. down the road. I’ll break out the crayons and doodle something up.
See attached sketch. Headlight alternate wiring method
The Idea here is to keep the stock wires up to the female connector intact. The L wire will need to be cut 3 inches past the male connector, the other three wires remain intact.
The L wire (12V signal) will go to one side of the coil on the new relay. The other side of the coil will get a new ground wire from the battery. This ground wire can also be ran to your low beams, or new HID lights. Install a fused 12V, and wire it to one side of the contact. The other side of the contact will now give you a proper 12V switched power source, that can go to your headlights/HID lights.
Below, page 466 blown up for reference.