I have a 2017 Triumph Tiger Explorer XRx, and need to find a wire that can act as a switched power source. My aftermarket lights (Denali D4) are connected directly to the battery, but I need a switched power source to trigger the relay.

I'm having trouble finding wiring diagrams for the motorcycle online, and don't know where to purchase a service manual.

I cut open the wiring harness that goes to the back of the bike, but can't figure out which wire I should tap into, using a posi-tap.

Question: Can someone point me to a wiring diagram, or let me know which wire can be used to act as a switched power source, underneath the pillion seat?

  • What type of switched power source? sidelight? headlight? Ignition? Braking? I would start by identifying what colors do - using a test lamp (low power) or a multimeter - but a test lamp tends to be quicker for this as you don't have to "read" the light as you do a multimeter... – Solar Mike Oct 6 at 22:51

In the wiring harness that goes to the back of the bike, one wire will carry switched current: the wire that feeds the tail (not brake) light — it's always powered when the ignition is on. If you can remove the tail light assembly, you may be able to see what color pattern that wire has — it's the wire that connects to the tip of the bulb.

If you have a voltmeter, you can find the wire this way. Connect one lead to ground, and the other (I'm guessing the leads have alligator clips on the ends) to a sewing pin. Turn on the ignition. Then using the pin, probe gently through the insulation on each wire. One wire will be carrying current, and will register on the meter. That's the wire you want.

If you don't have a voltmeter, make a test rig out of a small 12v lamp. Get a foot-long piece of wire and strip several inches of the insulation off both ends. Wrap one stripped end around the base (not the tip) of the lamp. Wrap the other stripped end of the wire around the sewing pin; this won't be a great electrical connection, but it should do. Again, turn on the ignition. Hold the tip (not the base) the bulb onto a bare metal part of the frame; your other fingers can help hold the wire that's wrapped around the lamp base. With your other hand, use the pin to probe into the wires of the harness. When you touch the live conductor, the lamp will light.

  • Using an old bulb holder would make the test lamp so much easier to use and safer as well... I mean what you describe is not even Heath Robinson... – Solar Mike Oct 7 at 19:35
  • @SolarMike <g> You're absolutely right. From the tenor of the original post, I assumed that an old bulb holder would likely not be at hand. – David Oct 7 at 20:46

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