De link third brake light from pedal

Willsmotorcycle

Willsmotorcycle

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Oct 26, 2020
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Location
Makefield Highlands PA
Bike
2016 ST1300P
2025 Miles
000545
Greetings all, I was wondering if anyone has third brake light that they only operate with the lever.

I have an 07 and above ABS P and a LIN 3 strobe. Currently it is operated with the brake light but I would like to isolate it so it only works with the lever. Reason being at a stop light I use the pedal and won’t be annoying the drivers behind me.
 
Willsmotorcycle said:
Currently it is operated with the brake light but I would like to isolate it so it only works with the lever. Reason being at a stop light I use the pedal and won’t be annoying the drivers behind me.
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You can insert a diode between the front switch's switched terminal and the wire it feeds, and feed the third light from the same front switch terminal.

The diode's insertion point can be anywhere along the wire from the front brake switch to before the point where the rear brake switch is teed into it (buried somewhere in the harness, no doubt).

That way, both switches will operate the bike's brake lights, but only the front switch will operate the strobe.

I would suggest looking for a diode rated at 5a or higher and 50v or higher. Schottky diodes are a suitable type, too.
 
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Willsmotorcycle said:
Greetings all, I was wondering if anyone has third brake light that they only operate with the lever.

I have an 07 and above ABS P and a LIN 3 strobe. Currently it is operated with the brake light but I would like to isolate it so it only works with the lever. Reason being at a stop light I use the pedal and won’t be annoying the drivers behind me.
Click to expand...
On my ST there was a small amount of play in the rear brake light switch so that I could apply a very slight amount of brake and not trigger the brake light switch and the strobe light. Unless I was on a fairly steep grade it was enough brake pressure to hold the bike from rolling. My Goldwing is the same way.
 
Larry Fine said:
You can insert a diode between the front switch's switched terminal and the wire it feeds, and feed the third light from the same front switch terminal.
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I know this is a brilliant answer, I just don't understand it. Could you explain like I am a golden retriever?
 
Willsmotorcycle said:
I know this is a brilliant answer, I just don't understand it. Could you explain like I am a golden retriever?
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I'll try. "Woof! Woof-woof! Woof-woof! Woof!" How was that?

Okay, serious answer: The two brake-light switches are wired in parallel, so either one can trigger the brake lights. Switches that are wired in series must all be closed at the same time for current to flow in a circuit, such as starter safety switches.

One side of both switches receives constant power (they're both fed from the same wire), and the other side of both switches runs to the brake light bulbs (both feed the same wire), and is only hot when you apply either (or both) brake(s).

What you want is an additional wire that is only hot when the front brake is applied, so you need to receive power from the front brake switch that the rear brake switch does not also trigger. So, insert a diode between the two brake switches.

A diode is a device that passes DC in only one direction, and are rated by (reverse) voltage and (load) current. Most diodes are marked with a triangle pointing at a band, or just a band alone. The banded end should point toward the load.

If you were to pull the switched wire (hot with brake applied) off of the front brake switch, and attach the wire to the strobe to the terminal, the front brake would only activate the strobe, and the rear brake would only activate the bike's brake light.

Get that so far?

Now, by putting a diode between the front switch's switched terminal and the bike's original switched wire, the front brake can simultaneously activate both strobe and brake lights, but the diode prevents the rear brake switch from activating the strobe.

If you hit only the front brake, current will flow both to the strobe (directly) and to the original brake lights (through the diode). If you hit only the back brake, current will flow to the original lights (directly), but not to the strobe (blocked by the diode).
 
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Larry Fine said:
I'll try. "Woof! Woof-woof! Woof-woof! Woof!" How was that?

Okay, serious answer: The two brake-light switches are wired in parallel, so either one can trigger the brake lights. Switches that are wired in series must all be closed at the same time for current to flow in a circuit, such as starter safety switches.

One side of both switches receives constant power (they're both fed from the same wire), and the other side of both switches runs to the brake light bulbs (both feed the same wire), and is only hot when you apply either (or both) brake(s).

What you want is an additional wire that is only hot when the front brake is applied, so you need to receive power from the front brake switch that the rear brake switch does not also trigger. So, insert a diode between the two brake switches.

A diode is a device that passes DC in only one direction, and are rated by (reverse) voltage and (load current). Most diodes are marked with a triangle pointing at a band, or just a band alone. The banded end should point toward the load.

If you were to pull the switched wire (hot with brake applied) off of the front brake switch, and attach the wire to the strobe to the terminal, the front brake would only activate the strobe, and the rear brake would only activate the bike's brake light.

Get that so far?

Now, by putting a diode between the front switch's switched terminal and the bike's original switched wire, the front brake can simultaneously activate both strobe and brake lights, but the diode prevents the rear brake switch from activating the strobe.

If you hit only the front brake, current will flow both to the strobe (directly) and to the original brake lights (through the diode). If you hit only the back brake, current will flow to the original lights (directly), but not to the strobe (blocked by the diode).
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You had me at woof.

I read a bunch about them last night and watched a video that made my head spin. Reread your original post 20 times and now with this and the schematic from @spiderman302 I am anxious to mod it up. Thank you!!


BTW does anyone out there need 19 5a 60V diodes? ;)
 
And there's another way....

Put a pressure switch in and run it to the 3rd bake light only. It goes into the front reservoir thru the brake hose in place of the OEM banjo bolt.

That leaves all the OEM stuff and flasher circuit separate.

I don't think the linked braking on the ST backfeeds pressure from the rear system to the front for safety reasons. If it does feed pressure then this wouldn't work.


1633431639808.png1633431815675.png
 
spiderman302 said:
St1300BrakeDiode.jpg
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Exactmundo!

The diode doesn't have to be wired in at the switch itself, but can be wired in anywhere ahead of where the green/yellow wire from the rear brake switch is spliced to the one from the front.

I envision that the point where the right-side handle-bar wiring's 9-pin plug plugs into the bike's main harness is a good, hidden place.
 
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All you did is feed the strobe through the diode instead of directly. This presumes the aqua-colored wire feeds the strobe.

Look at Spiderman's diagram again. Note that the diode is inserted in the green/yellow wire, not merely attached to it.

1633558679989.png

This means that you have to actually cut the green/yellow wire. Then, connect the cut end coming from the brake switch and the strobe's wire to the diode's top terminal. Then, connect the lug on the threaded end to the cut end going into the harness (to the back brake switch and the brake lights).
 
Willsmotorcycle said:
That was a little funny, I didn't want to cut it until I knew it was right... It works perfectly, thank you, wag wag.
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Well, that didn't take you very long. Glad it works. :thumb:


What's important is understanding the logic of the modification; why it works.

That's a hefty diode you bought, by the way. It shouldn't need a heat sink.

Remember to insulate the body well, though.
 
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