I found several forums posting simple circuits to make a run/brake setup and decided to try this with the facia tri-bar led I installed on my Road King.

The simple circuit consists of two diodes and a resistor, costs less then $3, and works very well. And the small circuit fits easily in the tail light housing.

Parts:

2 - 1 amp Schottky Diodes - $2 (You must use Shottky diodes as the Vf, voltage drop, is a lot less then typical diodes. Otherwise, the tribar led at max brightness will be dimmed)
1 - 33ohm Resistor - $1.19 (two pack. I used a 33ohm 10 watt. You can try different ohm resistors to control running light brightness which in turn creates the contrast from run to brake)

Attached is a diagram from another site. Their are many on motorcycle and auto forums. But, they did not use the Schottkys. Trust me, you will want to. Also, ignore the resistor value. Depending on the diodes used and voltage drop, I'd say any resistor from ~25-45 ohms should work. But, try different ones to see what you prefer. The Schottkys I used had .33 voltage drop. The tribar led only draws about 100ma at 12v. When I made the circuit I put the resistor on the anode side, positive side, of the diode and used spade connectors to connect to the run and brake wires on the tail light.

I bought a 20 pack of diodes for $2.50 (Vishay). The 20 diodes will be used for other run/brake circuits such as tour pack leds and creating more contrast for Custom Dynamics led turns. And since the diodes are so inexpensive, I am pairing up all diodes in parallel for redundancy.

http://www.ebay.com/itm/272134450282...%3AMEBIDX%3AIT

Lastly, you can buy similar circuits but they are designed for specific led requirements and you may not get the desired results. And besides, its kind of a kick to play with electronics

 

Or you could buy one of these that has led's for the taillight, brake lights and turn signals. Just splice it into the stock wiring at the rear, no other parts needed. It cost me $35.00 with the shipping and has worked great for the last year.

http://www.t-motorsports.com/smoke-t...rley-davidson/

 

Yes, have seen those. Lots of options. The HD tribar lighting looks nice as the individual leds are not obvious and it has a glowing, albeit very bright, look to it.

Update:

I have been pm'ed asking for pics and more detail. I did not take any but the attached pics should help understand how it is wired. The resistor I used was 10 watts so it is larger then the one in the pics. The wire labeled "donuts" goes to the positive tribar wire. The tail lamp brake wire is red, and running light is blue. Tap into those with wire taps or solder, whichever you prefer. The tri-bar light power is directional so positive and negative do matter, unlike a typical bulb. If you are not sure which is positive, no problem, you wont hurt the tribar. Just switch the tribar wires if the tribar does not come on the first time. I dont remember the tribar wiring code, I think the positive had a stripe.

Update 2:

Added a couple pics. Run only, then with brakes applied. Nothing crazy, but a fun $3 mod making all lights go bright when brakes applied..

 

Thanks for posting those pics. Helps to get an idea of what you mean. I am very interested in doing this and I am going to have to make sure I get all the correct parts. Thanks for taking the time to post this mod.

 

......or you could make one for $3.

Thanks to the OP for the very nice explanation and diagrams. This is something even my disaster prone DIY butt might try out.

 

Very cool mod compared to the 100+ dollars they want at the dealer to do the same thing.
Thanks for sharing the mod.

 

Kuma,

Which part number is your tri-bar?

I was just about to order the Custom Dynamics one, but I've read mixed reviews...

Thanks!

 

I also used the diodes to create more contrast with custom dynamics led clusters. The cd leds blend in better now with the other leds in run mode and their is A LOT more contrast from run to brake. The wiring and circuitry is more complicated then this tri-bar mod though. Custom Dynamics sells a r/t/b module that allows you to adjust the contrast for ~$100.



I bought an 09 SG fender take off. Facia panel, tri-bar light, turns light bar and smoked led tail light are off of that.

 

Thanks KumaRide for the great write up and the pictures sure help me.

My parts are ordered and I will work on this next week.