K75 Project - Tail Light/Stop Light Wiring

[stuman]

Hi,

I'm hoping for some advice regarding how to wire up a new LED tail/stop light.  I have completely stripped my 1991 K75 RT to just the frame and I will be fitting the tail/stop light attached!!

I have attached a picture so you know what wires I have.  As you can see it goes like this:

Black = Ground
Yellow = Running
Red = Stop

On my RT currently I have 4 wires.  2 Brown power wires going to the running and stop connectors and then each one has what I assume are the switch wires.  All my wires are labelled so once I know what to do it will be straight forward.  My question is how to wire the existing 4 to the new 3?

I'm thinking remove 1 of the brown power wires (easily done) and connect the remaining brown to the Black Ground wire and then the other 2 wires to the respectively (stop to stop, running to running).  That cool?

Also do LED tail/stop lights need a load resistor like turn signal lights do?

I will be working on this at the weekend so I'll just give it a go but I thought I'd ask the much wiser Motobrick community first.

Any help or advice gratefully received.

Thanks
Stu

[stuman]

Or is the ground a true ground and need to attach to the frame?

[johnny]

1 brown is negative for tail...

1 brown is negative for brake...

can just use 1 brown for both tail and brake negative...

the other two are prolly positive for tail and positive for brake...

look at a diagram or put a meter on there...

[stuman]

Thanks Jonny

Sure but how do I get 4 down to 3 and what goes where?

Cheers
Stu

[johnny]

greetings...

this is whack... im out...

j o

[stuman]

yeah mines a '91 but thanks anyway!

[rbm]

Black => Brown (Ground)
Yellow => Grey/Black (Running +ve)
Red => Grey/Yellow (Brake +ve)

Choose either Brown wire because they are both ground.  Leave the remaining Brown wire unconnected.

Also do LED tail/stop lights need a load resistor like turn signal lights do?

You will need to modify the Bulb Monitoring Unit to make it LED friendly, otherwise it will always light the warning indicator in the dash.

[stuman]

Hi rbm,

Thanks for confirming. I thought that might work!  I was aware of the bill monitor unit but I am swapping put my dash for a single round gauge so not sure if I'll have a warning light but I guess I will.  That new gauge and the bulb monitor unit are further down the road tasks...

Thanks again!
Stu

[stuman]

Ok that worked!  Connected as I thought and as discussed above and my running light came on when I turned my lights on and my brake light worked when I hit the brake.

Well for a minute.....then they just stopped working.  Anyone know why this could have happened?  I wouldn't have blown a fuse would I?

Thanks
Stu

[rbm]

So, you removed the BMU and jumpered the wires on the socket?  Or did you do something else?  Have you inspected the fuses yet?  It might be fuse #1 that could have blown.  If fuses blow, then there is a wiring error somewhere.  Have you rechecked your modifications, or looked for a pinched wire?

[stuman]

Hello again rbm,

No, didn't touch the BMU just connected the wires correctly.  I haven't checked the fuses yet but I will be tomorrow. I'm not actually final fixing yet and I just did this quickly today I need to do some welding to the frame and tail tidy before I actually fit and connect it permanently; today was just a test fit.

None of my modifications so far have meant I have really touch any wires although I did just pinch the connectors to my new tail/stop light connectors.  So it could be crappy connections or a fuse and I'll check those but could it be anything else?

Thanks
Stu

[rbm]

I'm not sure if the BMU is smart enough to cut power to the brake light when failure is detected, but it might have.

Just to clarify one thing, did your running lights also stop working the moment you tested the brakes? Did you test only with the front brake (then it failed), or with the front then the rear brakes (then it failed)?

btw, Did you disconnect the battery, undo all grounds and disconnect all electronics before welding?  If not, I hope they survived the ordeal.

[stuman]

Hi,

Yes running light and brake light stopped at same time.  I didn't even touch the front brake actually now you mention it! 

I haven't done any welding yet so I haven't disconnected anything.  Just lining everything to start so as it stands the bike is as it left the factory.

Thanks
Stu

[rbm]

It is possible that the brake switch wire is pinched under the footpeg plate if you have removed/reinstalled the plate during your rebuild.  It might also be possible that the temporary wiring setup you used experienced a short circuit with the exposed terminals.  Check those possibilities.

[stuman]

Hi, again I haven't removed anything so no chance of pinching the wire anywhere else on the bike....but yes I just hooked up exposed terminals so I'll do them properly next time and check the fuses.

Thank you very much for your thought's.  It's good for me to talk things through!

Thanks
stu