Remember that their wiring diagram is designed with Harley-Davidson® in mind and using the H-D stock 
switches. Using the custom controls will require a little modification, but the guys at Thunder-Heart are 
so bike and electronics savvy that they can walk you right through almost any installation, AND they’re 
super nice guys!

The difficult part of this wiring job is using the momentary switches that come with the BDL, Performance 
Machine petite handlebar controls kits and most other cool custom handlebar controls. You will need to 
use two relays to make these switches work as on/off switches. A small sacrifice considering the BDL 
controls are so smooth, trick and cool.

In a brief phone conversation with Thunder-Heart, I was told they will have a small in-line circuit board 
that does the same thing and takes up a lot less space probably before this article goes to print. So be 
sure to check with your dealer and specify Thunder-Heart.

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This fun took a week to finish to satisfaction. I cut and re-did it three times. 

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Don’t forget, you’ll need a horn to be legal. Here I’ve mounted a small 12 
volt, 2-1/2” chrome one that I got from Custom Chrome on a piece of cut 
angle bolted to the transmission mounting bolt. This is another thing that 
takes pre-planning. You will need a least a 1/4” longer 3/8” bolt for this 
hole as you will also want to use a cable holder to hold the wiring harness 
up under the frame in place. 

Fishing for wires is never any fun, but one of the tricks I’ve learned is using a piece of string.

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Feed a piece of string through the hole where the 
switches will go, tape off the other holes, then blow 
air thru and the string should come out at the bottom 
of the riser hole. You can also use a vacuum cleaner 
and suck the string through. Either way works.