Wiring brake/tail light - any time I close a circuit the horn sounds! Please help with the troubleshooting...

[romandesign]

I got a new Wheelspeed Taurus ebike that doesn't come with a tail light. It has an S830 display. I ordered some colour Y-cables to tap into the cables without cutting anything, and a 48V tail light with running light, brake light and turn signals. I found a couple of combinations of ground and +48V with a multimeter. And when I close circuits with a tail light it works fine, as long as S830 is off. But if I turn S830 on, and close any of the ground-to-+48V circuits with the tail light the electric horn sounds!!! I don't get it, because it happens even if I don't use the blue cable (that goes to the headlamp and horn).

Now I'm lost... I got 3 Y-cables, and here's how I intended to wire it. Blue cable goes to headlamp and horn, yellow to swithc with headlight and horn buttons, red to the right brake lever. But something doesn't add up...

 

[amberwolf]

To find out what is happening, you'd have to trace out and/or continuity test where each wire in your system is connecting on each device, and draw that up and post it here, along with the specific items that are being connected to and what each wire is intended for. (not just the cable, but the specific wire and pin on each cable).

Just knowing what voltage is there isn't enough, because you don't know *why* that voltage is there, what it's internally connected to, etc. Knowing *where* each wire connects, then determining the function of the specific place that wire connects, can be used to be sure of the correct wiring for the functions you want to happen.

 

[slaphappygamer]

Definitely something is shorting out. I would start at the horn. Unplug the horn/headlight and meter towards the controller. First with the display off, then with the display on. You should see a difference. Note what the difference is. Wondering if the Y adapter has transposed wires. This may be a way to tell.

Before you do this, has the horn ever worked? Or is this the first time you are setting it up?

Also, would be worth setting up your meter towards the headlight as well. Perhaps the headlight is defective.

 

[romandesign]

Before you do this, has the horn ever worked? Or is this the first time you are setting it up?

Yes, when connected as is, everything works fine, horn/headlamp switch turns things on etc.

I'm thinking about maybe tapping the battery directly somehow, instead of Y wires. It's all neatly connected inside the frame, but maybe I can find a place to tap near the controller or where the contacts for the removable battery are. I'd have to place a fuse in line (I only have 12V fuses, but I guess it would still work for a short) and place a separate end switch for the brake light, instead of tapping a brake lever switch as I wanted to... But maybe it's gonna be safer that way. I'm afraid that it's too complicated to trace everything, and I don't want to short and burn the display or controller, just want to add a tail light...