Topic: Wiring a standalone license plate light?

[aperry]

Probably an easy question for someone, but I'm having trouble understanding the following behavior with my 750 K3:

I have wired in a pair of license plate light "LED nuts".  These are neat little license plate mounting nuts with downward facing LED lights that illuminate the license plate.

I thought it would make sense to use the tail light wires for this, so I added the right connectors to the Brown and Green wires that run to the tail light and connected the new LED lights to that.  At first glance it seemed to be working fine.  However I've noticed that whenever the brake light comes on, the license plate lights turn off.   I'm having trouble understanding why this happens.  In the wiring diagram it looks like the brake light and tail lights are on separate circuits, so I don't understand why they behave this way.

Any ideas?  If you've done this, how did you wire it?

I probably could just tap into one of the black ignition switched wires and have these little lights on all the time, but I'd prefer to have them on only when the headlights/tail lights are on.

Thanks!
Aaron

[bollingball]

When you apply the brake and the new LEDs go out does the tail light go out also? Try taking off the brown going to the bulb leave the LEDs hooked up and see if they work. I have read where LEDs and incandescents don't mix. But there is a work around. Try what I said and let us know what happens

Ken

[bollingball]

http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fled_prods.htm

This place will have what you need Someone who has done this will chime in. I think you need a load reistor but not sure if that is what you call it. Where are all you LED guys 

Ken

[aperry]

When you apply the brake and the new LEDs go out does the tail light go out also? Try taking off the brown going to the bulb leave the LEDs hooked up and see if they work. I have read where LEDs and incandescents don't mix. But there is a work around. Try what I said and let us know what happens

Ken

Hi Ken,

Ok, this bike does have a mix of incandescent and LED (and I bought an electronic flasher unit to handle the turn signals).  My brake light and tail light are a single LED unit that has three leads to handle low brightness (tail light) and high brightness (brake light).  When I apply the brake, the light gets bright (as expected), and the license plate LED lights go out.  They come back on when the brake is disengaged.

I will try your test shortly and report back.  Thanks for the tip.

Aaron

[aperry]

Hmmmm, I got a result that I wasn't expecting.  My LED brake/tail light has three leads (red, white and brown).  I have brown connected to the harness brown (tail light), and red connected to the harness green/yellow (brake) and the white is connected to the harness green (ground).  I suppose this could be wrong, but everything was working nicely until these license plate lights came along.

Interestingly, when I disconnected the brown wire to the tail light, nothing changed!  The tail light still worked, the brake light still worked, and the license plate lights are working but they still turn off when the brake light is engaged. 

So I'm a little puzzled by this.  I don't see how the green/yellow brake light wire can handle both brake and tail.  Maybe I'm not understanding the wiring diagram, but it seems like green/yellow should not be getting voltage when the brake switch is open.

Aaron

[Gurp]

I would prolly run a hot wire from the +going to your headlight switch and ground from the frame. It would come on anytime the headlight is on that way.

[bollingball]

Probably an easy question for someone, but I'm having trouble understanding the following behavior with my 750 K3:

I have wired in a pair of license plate light "LED nuts".  These are neat little license plate mounting nuts with downward facing LED lights that illuminate the license plate.

I thought it would make sense to use the tail light wires for this, so I added the right connectors to the Brown and Green wires that run to the tail light and connected the new LED lights to that.  At first glance it seemed to be working fine.  However I've noticed that whenever the brake light comes on, the license plate lights turn off.   I'm having trouble understanding why this happens.  In the wiring diagram it looks like the brake light and tail lights are on separate circuits, so I don't understand why they behave this way.

Any ideas?  If you've done this, how did you wire it?

I probably could just tap into one of the black ignition switched wires and have these little lights on all the time, but I'd prefer to have them on only when the headlights/tail lights are on.

Thanks!
Aaron

So now you tell us the brake/tail bulb is also LED. It is hard to help when you leave things like this out Any thing else we need to know.

Ken

[xnewmanx]

Probably an easy question for someone, but I'm having trouble understanding the following behavior with my 750 K3:

I have wired in a pair of license plate light "LED nuts".  These are neat little license plate mounting nuts with downward facing LED lights that illuminate the license plate.

I thought it would make sense to use the tail light wires for this, so I added the right connectors to the Brown and Green wires that run to the tail light and connected the new LED lights to that.  At first glance it seemed to be working fine.  However I've noticed that whenever the brake light comes on, the license plate lights turn off.   I'm having trouble understanding why this happens.  In the wiring diagram it looks like the brake light and tail lights are on separate circuits, so I don't understand why they behave this way.

Any ideas?  If you've done this, how did you wire it?

I probably could just tap into one of the black ignition switched wires and have these little lights on all the time, but I'd prefer to have them on only when the headlights/tail lights are on.

Thanks!
Aaron

So now you tell us the brake/tail bulb is also LED. It is hard to help when you leave things like this out Any thing else we need to know.

Ken

I doubt it's going to make much difference in this case.


OP:
Are there only 3 wires coming from the taillight?

Do you have a multimeter available?

[aperry]

So now you tell us the brake/tail bulb is also LED. It is hard to help when you leave things like this out Any thing else we need to know.

Ken

I certainly would have included it if I thought it mattered at the time.  In fact, I'm still confused as to why this matters (regardless of the weird tail light behavior that I've noticed). 

Like I mentioned earlier, the wiring diagram seems to indicate that the tail light is on whenever the headlight switch is on, and the brake light is on when either of the brake switches is activated.  As far as I can tell, it does not show any switch that would turn off the tail light when the brake lihght is active.

Aaron

[aperry]

I doubt it's going to make much difference in this case.


OP:
Are there only 3 wires coming from the taillight?

Do you have a multimeter available?

Yes, and yes.  The tail light is an aftermarket LED light with lead wires.  It is capable of two brightness settings.  The wires are red, brown and white.

[aperry]

I would prolly run a hot wire from the +going to your headlight switch and ground from the frame. It would come on anytime the headlight is on that way.

This seems like a good solution.  I was hoping to avoid running another wire to the bucket, but that may be the best way to go.

Incidentally, I ditched my starter motor (and solenoid) and now the bike is kick-only.  According to the wiring diagram, I should have an empty ignition switched black wire that powered the solenoid.  It should be in rear of the bike already.  I was hoping to get the bike inspected tomorrow.  So Maybe I'll just see if I can switch the wire into that one for the time being.  The lights would be on whenever the bike is on, but I think it's a negligible number of watts and they're pretty hard to see in daylight anyway.

Aaron

[xnewmanx]

I doubt it's going to make much difference in this case.


OP:
Are there only 3 wires coming from the taillight?

Do you have a multimeter available?

Yes, and yes.  The tail light is an aftermarket LED light with lead wires.  It is capable of two brightness settings.  The wires are red, brown and white.

My speculation would be that the tail light brown wire is ground.  The thing about LEDs is that if you hook them up in reverse, the brightness is different, so you could have a forward and reverse current thing going on that's changing the brightness of the light.  That's why it still works with the brown wire disconnected.

My GUESS is that the LED tail should be hooked up:

BIKE:TAIL
Br:W
G:Br
G/y:R

In all my years doing car/bike stuff I have NEVER seen a white ground wire. 

Also, there is ZERO reason that you should have to run a dedicated wire for this.

[aperry]

Xnewmanx, I like that theory and I will take a look at that possibility when I get home from work.  Although I've managed to get the whole bike working, I wouldn't consider electrical to be a strong point of mine.  I'll check this out later today.

Aaron
 

[superseven]

So to summarize all is working until the brake light is turned on.  I am thinking the application of the brakes opens the circuit somehow.  This would suggest the the brake light gets its return path path when the brake is applied and the taillight looses its path.  Is it possible that the LEDS are also getting a ground via the frame thought the nut itself or is the assemble plastic?

I would place a meter on the various circuits and try to figure out what is happening.  Keep in mind a Led will only light when the current is flowing in the right direction so if anything changes the direction of flow they will go out.

If I had to guess not having a diagram I would say that you could just tap into any ignition switch controlled positive 12v line tail light included and just ground to the frame local to the plate mount.

[superseven]

Just another thought my guess is that the tail light and brake light are in series throught the brake switch to ground (need a diagram to confirm) when the switch is pressed the brake light is introduced into the circuit meaning if the LEDs are wired across the tail light they will loose the required forward voltage drop and turn off. 

Ground to the frame and try again.

[aperry]

Thanks superseven.  The tail/brake light itself cannot be grounded by it's mounting hardware because it's mounted to a fiberglass seat cowl.  However, after disconnecting the brown wire, somehow the brake/tail seems to continue functioning properly as both brake and tail with only two wires. So it's a bit of a mystery to me.  I don't have the wiring diagram in front of me, but last night it did not appear that brake and tail are on the same circuit on the Clymer diagram (which is the clearest one I've seen).  Admittedly I think I'm reaching the extent of my electrical knowledge.

I think your advice to start using a meter on all of this makes perfect sense.  Last night's testing was a bit hasty, so I'll spend some more time on all of this tonight or tomorrow and I'll start writing down what I see for voltage at the various wires in play, between tail light and brake light.

Aaron

[aperry]

Figured I would ask the eBay seller of the tail/brake light about the wiring.  His response:
"The white wire is your ground, red turn and brake, brown running light."

Looks like I had that wired correctly.

I'll need to take a meter to the harness leads and see what happens to each wire between brake and no-brake.

Thanks,
Aaron

[xnewmanx]

The taillight circuit is pretty much as simple as it gets and unless someone screwed with the harness, is in no way affected by applying the brake.

The power path for the tail light circuit goes:

Battery
(r/y) then (r)
main fuse
(r)
ignition switch
(b)
headlight switch
(br/w)
back through another circuit in the ignition switch
(br???)
tail fuse
(br)
tail light
(g)
ground

The brake light:
battery
(r/y) (then r)
main fuse
(r)
ignition switch
(b)
brake switch (front and rear are in parallel so that either switch completes the path)
(g/y)
brake light (g)
ground

if the tail light is ON when the brown wire is disconnected that means there is power coming from either the green wire (oem ground) or the Gr/Y brake circuit light.  Neither of these should have +voltage when the brake switches are not closed. THIS IS A PROBLEM.

Now, LEDs typically don't dim.  They will abruptly shut off if the forward voltage drops too low.

I assume that your battery is sufficiently charged, so the next step would be to measure the voltage at the brown wire where it is joined with the tail light.  See if the voltage drops substantially when the brake light is depressed.  Try this both with the tail light connected and not connected.

Another test, just to help rule out anything weird, temporarily ground the license plate light's ground wire directly to the battery.  If you're somehow getting reverse current through the light somehow, this should help troubleshoot it.


WE CAN DEFINITELY SOLVE THIS.