auxillary brake light

[Pat Kelly]

I'm trying to add a brake light on my trunk. This would be similar to the 3rd brake light on a car.

On my 78 E model I traced out the yellow/green wire and poked it with my tester. When contact was made the tail light went out and the test light glowed faintly. When the brake was applied the brakelight on the bike lit up as did the test light.

Without poking into the Y/G wire the tail/brake light on the fender works as it should. The only thing I've modified is the bulbs themselves. I replaced the incandesent 1157 bulbs with LED 1157 (red) bulbs. These have been working on my bike since mid-summer.

Any XSive electrical engineers have any suggestions?

[TopCatGr58]

Hey there Pat,

I'm no electrical engineer, but after reviewing the colored schematic for your bike, there should be three wires going to your tail lights, the Yellow/Grn is the bright brake light, the solid Blue is the running light, and the Blk is the ground, if you are only using the Yellow/Grn for both running and tail, then something is wired wrong. There shouldn't be any power coming thru the Yellow/Grn "UNTIL" you apply the brakes!! You may have some more wiring to do to fix the OEM setup of your brake lights, then once you get that done, then it should be a piece of cake to add the extra tail/brake light, again LED is a good choice, that's what I'm running on BOTH of my light sets, my fender one and the one I have mounted high on my backrest at EYE LEVEL!
HTH, T.C.

[Pat Kelly]

That's what I'm not understanding. The auxillary (3rd) brake light is (to be) wired as only a brake light.
My stock tail/brake works fine until I tap into the yellow/green. Seems there should be no juice in the Y/G until I squeeze the brake. Looks like some time to be spent tracing wires.

I just got a wiring harness off Ebay. This looks to be in great shape. All the connectors are looking good and the PO did some work on the fusebox. Looks like they soldered in some robust ends that hold the fuses so it is still stock appearing but unlikely to break like our originals do/did. I installed spade fuses in my bike when I got it as mine were bad, but that was done on an individual basis and isn't pretty to look at. The fuseblocks posted in the repair section of the list are the way to go. Just haven't gone there yet.

Also picked-up an electrical oil pressure guage and that will be going in after I get the 3rd brake light working.

[John]

Hey Pat. The problem you are describing sounds like a bad ground. The voltage from the tail light circuit is back feeding through the brake light circuit, trying to find ground. Remove the black ground wire from it's attaching point and clean it, and the area that it is attached to on the bike. It grounds to the fender, doesn't it? I have a 78E but don't recall where the wire grounds to.

[Pat Kelly]

At the tail light it grounds to the housing. Everything works fine until I tap in under the seat, that's when the tail light goes out.
I'm going to start at the tail light and work my way back (front?).
I'll see if it changes anywhere along the way. I reall don't want to run a wire all the way from the tail light, under the fender, then up to the trunk.

[Pat Kelly]

it works, but at a price

I checked the wiring at the connector under the seat, at the tail light, and at the (rear) brake light switch. All resulted in the same thing, tail light goes out when tapping into the brake light circut.

I thought about what was different and followed the tan wire. I had replaced the flasher with a 2 prong electronic unit, maybe that was the problem. I put the original back in and had the same result. I next took out the LED-type 1157 bulbs and put the incandesent ones back in... it now works. I guess the LED bulbs share circutry that caused my problem. Maybe a diode in-line on my brake light wire or something like that would allow me to run the LEDs.

Now my charging system is back to marginal but I have the extra brake light. Safety or function, decisions decisions.

[Shadow]

Pat

Where I work we were trying to install some LED flashers on our equipment, and it didn't work. Apparently they don't draw enough amperage to activate the flasher unit, you might be able to find a resistor that allow the lights to work.

[Jerry]

You can get a commercial load equalizer. View one at:

http://www.jpcycles.com/shop/group.asp?GPID=3433

This one is marketed for Harleys but I have been told it will work on other bikes as well.

[Pat Kelly]

I was thinking of putting a diode in-line between the (LED) bulbs and where I tied in for the aux. brake light. That should keep the voltage from creeping back from the tail circut into the brake circut. If this seems like a solution then anyone be able to advise me as to what spec diode to go with?

[TopCatGr58]

Hey there Pat,

Well, when you put the standard 1157 bulbs back in, it all worked correctly, right? This tells me that your LED 1157's have some sort of short in their circuitry, cause it's a simple case of two different leads for tail and brake coming in to the socket and the actual socket as the ground! The LED 1157's are apparently not isolating the two circuits. Have you taken a meter to the LED 1157 bulbs? And I would think being designed for replacement of OEM that the LED 1157's should have the same pattern of the knobs on the side of the bulb, one low, one high to ensure that you don't get the bulb in backwards!?

I had no problem wiring the large array of tail/brake light LED's I put on my Special, they came with 3 wires. The turn signals don't even mix with the tail/brake light circuit. And using an electronic flasher works for using LEDs in turn signals so no fancy diodes or load equalizer is required, just an FYI! Good Luck!
T.C.

[POOLBOY]

Diode

You probably dont need the diode, but I commend you for your trouble shooting savy. If you need/want to try the diode, go to Radioshak and get one rated to carry 4 to 6 amp's.This is WAY excessive, but diodes are cheap.Voltage wont matter, as they will all be rated over the 14 volt's you will be dealing with.

[TonimusMaximus]

Just a question, when you're tapping in to the brake lights with the LED 1157s in, are you using a LED 1157 at the tap too, or a standard? The only thing I can think of IF the wiring is good, is that the standard incandescent 1157 should have less resistance than the LED 1157s. Electricity is lazy and takes the easiest path. Just a thought.

[POOLBOY]

Brake light circuit

Pat. Here is how it is supposed to work.
Starting at the battery,your 12 volts proceed's on a red wire to a fuseable link, also red.From there, it go's to the 30amp fuse on the left side of the bike. From the 30amp fuse it proceed's to the main key switch, still a red wire.
When you turn on the key switch, it connect's the red wire to the brown wire,and the blue wire.Yamaha seem's pretty consistent at this point at using brown to denote "Key On" wires.The brown and blue wire's now go to your fuse box fuses.The brown wire exit's the fuse box, and go's to your front and rear brake switch's(one on the handle bar, the other at the rear brake linkage to the master).It go's many other places as well, but for our discussion we are only concerned with the brake switch's.
The "output" of both brake switch's are joined together in the wiring harness.The wire color on the "output" of the brake switch's is green and yellow.This wire go's nowhere else except to your brake light.
The running light at the rear is supplied by the blue wire coming from the fuse box, to the rear light assembly.
The black wire is ground.
I suggest testing for a good ground,first. Then you could probe at the green/yellow wire's at your brake switch's with your test light. Nothing should chainge when you "stab" the green/yellow wire with your test light, untill you activate the brake's.
There is no reason you cannot run LED style light's on the brake circuit, as it is a simple switched feed.Current draw with a LED light could be an issue in a flashing circuit,such as a turn signel, but the brake light circuit is controled by the brake light switch's only.
Hope this help's.

**************************SPLASH******************

[Pat Kelly]

This is great input!!

The circutry you described is how I'm seeing it on the wiring diagram.

My test light (which did the same thing as the lights I hooked-up) is incandesent. The lights I've added are the inexpensive 'strip-lights' 6" long with 2 small lights in each strip. I don't think they're LED.

Before trying to hook-up the aux. light (and anytime it's un-hooked) the LED 1157 bulbs worked as they were supposed to, tail and brake.

After running this set-up for a day or 2 now I've concluded that these lights are not bright enough to use as a brake light. At night they really stand out but during the day they're insignificant. I guess I have no increased braking 'noticeability' but at night it seems more effective.
I see my options as:
1. Leave it as it is, safer at night, charging system works 'so-so'
2. Move it from the brake to the tail light circut and put the LED 1157 bulbs back in, increased visibility and charging system under less load.
3. Look for a different (LED?) aux. brake light that is brighter.

For now I think I'll go for option #2 and look into #3. The lights I put on look ok on the bike.

[TopCatGr58]

Hey there Pat,

Did you see my tech tips on the LED replacement lights conversion for the brake lights?? You mentioned that the strip lights are 6" long. The LED light set I used was 6" long by 2 1/4" wide, and provided both an additional running light, and a bright brake light level of illumination as well. Their housing was a bit thick, and so that could be a limiting factor on having a nice flush mounted look on your trunk, cause they are really designed to fit into the recess of a truck/tractor trailer oval slot, but they are fully enclosed, sealed, and have a nice clear red cover lens, and you could just drill a couple of holes into the base and screw them onto your trunk from the inside of the trunk, or you could GLUE them, double sticky tape them, etc.!! I provided the link to the web site where I got them, but you could also do a search for other lights. The web site had some wider/taller rectangular profile lights as well. And since they're LED,s they should work well with your LED 1157 bulbs!!! Just an idea!
T.C.