Installing a "Digital 5 Function Voltmeter"
on a Suzuki GS500 member Rema1000 introduced me to a neat gadget:

I ordered one from the California Sport Touring website. It's obviously intended for use in an automobile, but how cool would it be to have all of this functionality on a motorcycle? The feature that attracted me the most was the thermometer. I have been known to do some serious winter riding, and I've always wondered about the actual temperatures that I ride in. I already have a clock mounted to my bike, but it's unreadable at night. So I liked that aspect of the gadget too. The voltmeter was an added bonus for monitoring my battery and charging system.

Before even trying to mount the unit on my bike I REALLY wanted to have a way to quickly and easily connect and disconnect it. One reason was that I didn't trust it to be weatherproof. Another reason was so that I could move the gauge back and forth between my bikes.

This is the "permanent" half of the solution I came up with. I cut all 5 wires and used heat shrink tubing to bundle them together. Then I inserted the free ends (unstripped) into a 6-conductor RJ-11 plug and crimped them in place.

NOTE: The black wires attached to the as-purchased unit above are currently NOT crimped into the RJ-11 plug, for 2 reasons.

First, the black wires are too thick to fit into the plug. I tried shaving the insulation down so they would fit, but it was too much trouble for too little benefit, because...

...Second, they go to a remote temperature sensor, which allows an automobile driver to know the outdoor temperature. The main unit contains an internal sensor for the indoor temperature. Since both temperatures should be similar on a motorcycle, I decided not to worry about them for now.

Still, I left a usable length of the black wires inside the heat shrink tubing. I can always cut all of the wires shorter later and try again to crimp all 5 of them into a new plug. That's why I chose to use a 6-conductor RJ-11 plug rather than the more common 4-conductor one.

The rest of the solution involved adding a wire to the bike, and creating an "adaptor" to connect the gadget wiring to the bike wiring.

I learned on the message board that there are unterminated wires in the headlight bucket that could be used for adding certain accessories. (Gotta love that website!) One of the available wires is a connection to GROUND (negative), and the other is a switched POSITIVE wire that is energized only when the ignition is turned on. I still needed an always-on POSITIVE wire (so the clock would continue to keep time with the ignition turned off), but first I needed to make sure that what I had read was true for my bike.

I started by removing the headlight from the bucket. All I had to do was remove two Phillips screws and gently pull and twist on the metal ring surrounding the headlight glass.

This is what the "innards" of the headlight bucket look like. I ignored all but the two wires to the right of the clutch-side hole in the headlight bucket. They are hard to see in this picture, but they will show up more clearly later.
Having determined that I was "in business" as far as the NEGATIVE and switched-POSITIVE wires in the headlight bucket, I proceeded to add an additional unswitched POSITIVE wire.

I chose to attach it at the POSITIVE terminal of the starter motor relay. This is where the red wire from the battery is attached, and is out-of-the-way. I had to:

  1. Remove the right side panel.
  2. Disconnect the cable from the NEGATIVE battery terminal.
  3. Ease the starter relay off of its mounting tabs.
  4. Pull the 20-amp fuse cover to give me more room to work.
  5. Lift the red "boot" off of the connection that it protected.
  6. Crimp an appropriate connector to the end of a length of red "primary wire" - 18 or 16 AWG.
  7. Remove the nut, install the new connector, and replace the nut.
  8. Reinstall the protective boot and the fuse cover.
  9. Push the starter relay back onto its mounting tabs.
  10. Run the wire along the existing wiring harness bundle and up to the headlight bucket.
I made sure to allow enough length for the new wire inside the bucket.

Notice the two unused wires - they're encircled by the red wire in the photo. The black-and-white wire is the GROUND (or NEGATIVE) wire and the brown wire is the switched POSITIVE wire.

This photo shows my first attempt at hooking up an "adaptor cable". I made the cable from a length of the original orange/red/black wire that I had cut off of the "gadget". When I crimped the RJ-11 plug onto the three wires I made sure that each wire would match up with the wire of the same color from the "gadget". Then I used heat shrink tubing on most of the length of the wire, and crimped individual "bullet" connectors to the free ends. This was rather difficult because of the very small thickness of the wires. (24 AWG?)

Notice that I also crimped a "female" connector to the end of the new red wire.

As you can see, this arrangement did not last very long. The super-thin wires did not handle the crimping and the bike vibrations very well.
I needed a more more robust solution, so I decided to "beef up" the wires inside the crimped connectors. The photo shows the materials and tools that I planned to use for the improved solution.

In the center are short lengths of primary wire (18 to 16 AWG).

Clockwise from the upper right are:

  • A cheap soldering iron and stand from Radio Shack.
  • A roll of rosin-core solder intended for electrical/electronic work, also from Radio Shack.
  • The adaptor cable with its failed connectors snipped off.
  • Some heat shrink tubing, in two different thicknesses.
  • A butane torch for heating & shrinking the tubing.
  • A wire cutting/stripping tool.
I started by cutting the adaptor wires closer to the heat shrink tubing.
Then I CAREFULLY stripped the insulation from those tiny wires.
Using some "helping hand" tools to hold both of the wires, I soldered the thin wire to the thicker wire.


  • I should probably have wrapped a longer length of the stripped thinner wire around the thicker wire. Oh well.
  • Heat the wires, not the solder. I like to hold the iron to the BOTTOM of the joint. This works well for 2 reasons: The heat rises from the iron, and the solder can be applied on the top of the joint without obstruction.
  • Touch the solder to the heated wires. If it doesn't melt, wait until it does.
  • When the solder melts, slowly push more solder into the joint until it is "saturated".
  • Try not to disturb the joint as you remove the solder and the iron. If the joint moves before it cools, apply the soldering iron so the solder will melt again. Repeat until the joint is able to cool down undisturbed.
There -- the first joint was done. Not beautiful, but serviceable.
After soldering all three wires I was ready to apply the heat shrink tubing. The plan was to use small-diameter tubing over each of the solder joints and then to use larger-diameter tubing to enclose all 3 joints together.
I meant to use a lighter to light the butane torch, then use the torch to shrink the tubing. In the end I just used the lighter.
The adaptor was almost complete. All that remained was to crimp some "bullet" connectors to the ends of the new, thicker wires. It's hard to get a good crimp without a crimper tool. I found this one for $7 ... in the automotive aisle at my local grocery store!

The connectors that are included with crimper tools are invariably useless (or of insufficient number) for my purposes. So I bought a separate package of RED connectors.

Ready for crimping.
All crimped!

See the nice heat-shrunk bundle? Not only does it serve to insulate the joints electrically; it also provides strain relief by keeping the joints immobile.

I resurfaced from my basement workshop and reconnected the "adaptor" inside the headlight bucket.
Then I pushed the RJ-11 end of the adaptor through the throttle-side hole in the headlight bucket.
Finally, I attached the "gadget" with a pair of satisfying "clicks" and watched the panel light up.


All I have to do now is select the best place to stick some Velcro. That, and put the headlight back in the bucket....

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