Saturday, April 16, 2011

Project report: Installing an auxiliary brake light and turn indicator on a Vespa LX150

I promised to provide a project report and here it is. I know that many of you will appreciate this and that's why I'm taking the time to do it. It's more work doing the project report than actually doing the project.

Here goes.

This project report shows all the steps I took to install an AdmoreLighting Mini Light Bar LED auxiliary modulating brake light and sequential turn indicator unit on the Vespa OEM topcase on my Vespa LX150 motor scooter.

You'll see that I'm documenting my mistakes and clearly identifying them, so that others doing this project may not make the same mistakes. Not to worry though, there's always a way to get back on track.

  • Electrician’s pliers or wire cutter
  • Needle nose pliers
  • Wire strippers
  • Solderless connector crimper
  • Phillips screw driver
  • Soldering gun
  • Heat gun
  • Electric drill
  • 1/15 Drill bit
  • 9/32 Drill bit
  • Sharp craft knife, box cutter or scalpel
  • Voltage meter
  • A Sharpie fine-point permanent marker
1.  I planned to mount the Admore unit to my topcase.
I wanted to be able to remove the topcase without having to cut wiring connections.  The Reese trailer harness provides a good weather proof connector for that purpose.

2.  All the wire you’ll need for the installation comes with the Admore unit.  What you need to do is separate the wire in two parts, use the electrician’s pliers or wire cutter to cut the wire about 6 or 7 inches from the Admore unit.  On my unit there was a label on the wire.  Assuming that the labels are in the same place on all units, cut the wire just on the far side of the label, as you see in the photo below.
 3.  Cut the insulation sheath back a few inches, then strip each of the six wires about 1/4”.

4.  Cut the wires leading from each of the Reese trailer plugs about 1 1/2” or 2” from each plug and strip each of the five wires about 1/4”.
5.  Take the long section of wire you removed from the Admore Unit and, beginning at the end where you cut the wire, cut the insulation sheath back a few inches, then strip each of the six wires about 1/4”.

6.  As instructed in the Admore installation instructions that come from the unit, twist the blue wire and the red wire together.

7.  Cut five 1 1/2" lengths of 1/8 inch black heat shrink wrap and fit one on each of the wires you stripped in the preceding step.  Since the red and blue wires are twisted together, you only need five pieces for the six wires. 

This is where I made the first mistake. I forgot to slip heat shrink wrap onto the yellow wire before soldering it.  I unsoldered it, but the solder on the two ends of the wire prevented me from making a new solder joint.  So I shifted gears and used a solderless butt joint crimp connecter on the yellow wire.  Problem solved.   Hopefully by putting the heat shrink on all the wires before you start soldering, you’ll avoid my mistake.

8.  Notice that the two trailer plugs are not identical.  They are mirror images of one another.  One has five female connectors and one male connector, and other has the reverse.  On the assumption that one day you’ll want to travel without the topcase, select the plug that has the five female connectors as the one to solder to the long wire.

9.  Solder the wires to the trailer plug, matching the colors shown in the following diagram.
Click on the diagram to get a full size view.  You should probably also print the diagram out now, because you’ll be needing it later at the Vespa end of things.

Take care not heat the shrink wrap when you're soldering the wires.  In my case, I did cause a small bit of the shrink wrap to contract.  I used the box cutter (in my case, my scalpel [don’t ask, I’m a lawyer, not a doctor]) to cut away that small bit to allow the tubing to slide over the joint.
10.  Slide the heat shrink tubing over each solder joint so that each joint is insulated.

11.  Use the heat gun to shrink the tubing.

12. Starting from the other end of the long wire, slide an 8” or 9” piece of 3/8” heat shrink onto the wire and run it all the way to where the trailer plug is soldered on.  Bend the wires at the plug to bring them as close as possible to the plug, and slide the tubing as close as possible to the plug.  In my case, my scooter is Dragon Red, so I used red shrink tubing.  Since this piece of the wire will run from the scooter body to the topcase in plain sight, the red helps it look less obvious.  Just esthetics.

13.  Use the heat gun to shrink the tubing.

14.  Now carefully remove all the visible original black sheath off the wire and carefully separate the six colored strands.  Use your knife to cut away the fabric strands.  The easy way to remove the sheath is to slice it open where the shrink tubing ends, Get a hold on the six wires, and just pull them out of the sheath.  You won’t be needing the sheath, so discard it.

15.  Time to test your electrical skills.  Connect the two trailer plugs, the one you just soldered to the long wire, and the one you’re about to solder to the Admore unit.  Using a volt meter, check each wire for continuity between the very end of the long admore unit wire, to the stripped wires of the second trailer plug, the male one, making sure that all the connections work.  Congratulations, you passed your amateur electrician’s test.

16.  Now that you’ve soldered five joints successfully, you can tackle soldering the other trailer plug.

17.  Select the remaining trailer plug that has the five male connectors as the one to solder to the short wire coming from the Admore unit.

18.  Slide a piece of 3/8” heat shrink onto the wire from the Admore unit and run it all the way to the unit.  Make sure that the tubing is about 2” shorter than the sheath on the Admore unit wire.

19.  As instructed in the Admore installation instructions that come from the unit, twist the blue wire and the red wire from the unit together.

20.  Cut five 1 1/2" lengths of 1/8 inch black heat shrink wrap and fit one on each of the wires that come from the unit.  Since the red and blue wires are twisted together, you only need five pieces for the six wires.

21.  Solder the wires to the trailer plug, matching the colors shown in the diagram above.  Take care not heat the shrink wrap.  In my case, unbelievably, I made exactly the same mistake with the yellow wire.  There must be something in my brain with yellow.

22.  Slide the heat shrink tubing over each solder joint so that each joint is insulated.

23.  Use the heat gun to shrink the five pieces of tubing.

24.  Bend the wires at the plug to bring them as close as possible to the plug, and slide the black tubing down from the Admore unit as close as possible to the plug.

25.  Use the heat gun to shrink the tubing.

26.  Finally, all the lab tinkering is done.  What you now have is the Admore unit, terminating at the five-pin male trailer plug, and the other half of the wiring harness, terminating at the five-pin female trailer plug.
Now it’s time to head out to the scooter.

27.  Park the scooter in the center of your work space.  Set up some good task lighting.  If, like me, you’re working in a cold garage, lay a blanket down at the back of the scooter.

28.  Open the topcase, and remove the mat that lines the bottom.  Remove the large center screw, and then remove the topcase from the rack.  Bring the topcase indoors to your work bench or kitchen table.
29.  Open the seat and remove the pet carrier bucket.  Using the Phillips screw driver, remove the screw from the battery cover and remove the battery cover.  Make sure that you have a container to hold the screws you remove.

30.  Remove the screws that secure the plastic cover that surrounds the battery and the gasoline (petrol, for my UK readers) filler tube.

31.  Remove the gas (petrol) cap and gently lift off the plastic cover.  Once removed, replace the cap on the filler tube so that you don’t have to breathe in the high octane as you work, unless you like that smell and grew up sniffing gas for kicks.  No, seriously, put the cap back on.

32.  Next, still using the same screw driver, remove the single screw holding in each turn indicator light, pull the housing out, and let the housings dangle from their wires.

33.  Remove the two screws that hold the tail light in place, and remove the tail light, letting it dangle from its wires as well.
34.  Get the five Posi-Tap wire tapping gizmos out of the Admore unit parts bag, and install them onto the wires leading from the Vespa light housings following the wiring diagram above.
35.  Take the wiring harness terminating at the five-pin female trailer plug you completed in step 25, separate out the yellow and green wires.

36.  Take piece of 1/8” heat shrink tubing as long as each of the wires, less about an inch, and slide one piece each onto the yellow wire, and the green wire.

37.  Use the heat gun to shrink the tubing.  These wires will be fairly exposed to the elements inside the scooter’s body and that’s the reason for the extra protection.

38.  Now, looking down at the scooter from above, you’ll see that between the battery compartment and the back of the scooter body, there is an opening.  You’ll be feeding the three wires headed to the tail lamp through that hole.  On the opposite side of that hole, you’ll see an unused screw hole that leads into the battery compartment.  Thread the green and yellow wires from the hole at the back of the scooter, over the lip of the battery compartment, through the screw hole, and into the battery compartment.  Sounds confusing, but with the help of the photo, and seeing your Vespa, you’ll see what I mean.  Easy-peezy.
39.  Thread the yellow wire from the battery compartment, through the chassis hole nearest to the shock absorber screw, and down and through the left turn indicator opening.

40.  Do the same with the green wire, down and through the right turn indicator housing.  You’ll see that the inside of the scooter is pretty exposed and messy with road dirt and grime, and that’s why you added the extra insulation.

41.  Mount each of those wires to the Posi-Tap connectors that you installed at the turn indicator light housings in step 33.
42.  Now it’s time to tackle the part that took me the longest time until I figured a path out.  Fishing the remaining wires to the tail light.

43.  Turn your attention to the place where the tail light attaches to the scooter.  You’ll see that the wires come through a black rubber grommet.
Use your fingers or a pair of needle-nose pliers to pull the grommet out.  Slide the grommet back to the tail light housing that’s dangling free.  Now you can clearly see the rectangular hole into the scooter body.

44.  Get a three or four foot length of fairly stiff wire.  I used 12 gauge automotive wire, and it did the trick nicely.  Beginning at the opening at the top of the scooter, thread the wire into the opening and down towards where the tail light assembly is.  It takes a wee bit of trial and error, but eventually, you’ll catch a glimpse of the wire through the rectangular hole at the tail light end.  In the picture below, you can see the yellow 12 gauge wire going into the opening, and then coming out at the tail light end.
45.  Using the needle-nose pliers, grab the wire and pull it through.  Now, the toughest part of this project is done.

46.  Moving back to the opening at the top of the scooter, using electrical tape, tape the four remaining wires from the Admore unit wiring harness you made (the purple, black, blue and red wires) to the 12 gauge wire.  Moving to the tail light opening, gently pull the 12 gauge wire out through the rectangular opening until the Admore unit wires have been pulled through.  Here's a picture of the harness wires once they were pulled through the tail light hole, still taped to the 12 gauge wire.
47.  You can now remove the excess length of the Admore unit wires.  Cut the four wires so that you have enough to make the connections to the Posi-Tap connectors that you installed earlier at the tail light housing.

48.  Feed the four Admore wires through the rubber grommet, then push the rubber grommet back into place to seal the rectangular hole.
49.  Twist the red and blue Admore unit wires together, and then connect them to the Posi-Tap connector connected the Vespa wire with the black and yellow stripe.

50.  Similarly, connect the black Admore Unit wire to the black Vespa wire, and the remaining purple Admore unit wire to the Vespa wire with the black and white stripe.

51.  We’re almost done with the Vespa-side wiring.  Here's a photo of the new wiring harness with the battery compartment housing re-installed.
But before buttoning the scooter back up, it’s best to run a test.  Take the Admore unit and plug it in.  Make sure the kill switch is in the run position. Turn on the ignition.  The Admore unit should light up as a running light.  Now turn on the left, then right turn indicators.  The Admore sequential turn indicators should work.  Make sure the unit is right-side up so that the left indicator is on the left side.  Now apply one of the brakes.  The brake light should modulate, then stay on.  Release the brake and then re-apply it.  The brake light should come back on, but without modulating.

Here's a video of the test I did.


53.  You won’t re-install the underseat compartment parts just yet.  Let’s move on to the topcase end of things.

54.  In the comfort of your kitchen or workshop, turn the topcase upside down.  Take the Admore unit mounting bracket and figure out where you want to place it.

Here’s where I made another mistake.  I judged the location of the holes from the outside of the topcase.  Inside the topcase you’ll see that there’s a kind of trough that runs around the perimeter.  I ended drilling the holes a little too close to the edge of the trough.  I couldn’t get the supplied Admore mounting screws to sit flat as a result.  What I did was to mount the screws from below, with the nuts inside the topcase, and there was barely enough room.  I was lucky.  Make sure that the holes you drill as well within the “trough” so that there’s room to let the screw heads or nuts lie flat, whichever you prefer.

55.  On the outside of the topcase, use the permanent marker to mark the two mounting holes.

56.  Using the point of your sharp knife, make a small dimple in the topcase in the center of the mark, to give your drill a place to “bite”.

57.  Using your electric drill and your smallest drill bit (I used a 1/15 bit), drill pilot holes.  The topcase material drills nicely, I found that a low speed worked best.

58.  Switch to a 9/32 bit, and drill out the two holes.
59.  Using the screws provided with the Admore unit, mount the bracket to the topcase, and then mount the Admore unit to the bracket.
60.  Now re-attach the topcase to the Vespa, and plug in the Admore unit.

61.  Push any excess wiring harness wire into the opening at the top of the scooter.

62.  Remove the gas (petrol) cap, and, taking care not to pinch any wires, put the plastic housing that surrounds the battery compartment back on the Vespa.  You’ll see that there is a tab that fits into the hole you used to fish the wires down to the tail light.  That tab now has to share the hole with the wiring harness for the Admore unit.  That’s also the recess where the seat latch fits in.  So there’s now a lot going on in that hole.  As you re-install the housing, make sure you don’t pinch any wires, and use your finger to poke the wiring harness wires to the side, so they remain clear of the laching mechanism.  Once that bit of fiddling is done with, screw the housing down securely, taking care not to over tighten any screws.

63.  Drop the pet carrier bucket back into place, close the seat, and, finally, this project is done.

64.  Take a moment to congratulate yourself, admire the wonderful light show at the back end of your Vespa, show off your handiwork to your significant other, and then go for a ride.

Pheww... that was more work than actually doing the project.  I hope you will find the project report useful.


  1. Wow! Great job. I'll look into doing the same once I get my scooter back up to shape and on the road.

  2. Hi there, could you tell me what wires from the tail light harnes I would connect an aux brake light? I found the line that feeds the light but putting the wires does not activate the aux light. I have confirmed that the lights work. I think this is because I haven't properly identified the positive & negative lines & I cant find a diagram of the brake light wiring.

    1. See step 9 above and take a close look at the wiring diagram. The positive connection for the brake light is the wire that is black with a white stripe. You will also need to connect to the ground wire to complete the circuit for the brake light and that wire is solid black. I hope you get it sorted out.


The copyright in all text and photographs, except as noted, belongs to David Masse.