LED taillight (kz400)

Definitely don't want an unfinished project and am totally understanding there will be plenty of bumps on the road with a project like this (and an idiot like me working on it).

Where is the relay for the bulb failure circuit? Or do you mean just the bulb itself? Not sure if it's meant to work that way but the dash always lights up when I pull the brakes, even before any of this recent work.

The relay, I think it's causing much of your problem and if the light comes on every time you brake it doesn't sound like it's functioning correctly anyway. You will need to Look at the manual for it's location (unless anyone else with one of these bikes can tell you)

None of the bulbs in the instrument cluster should illuminate when applying the brakes, unless there is a problem.
The brake light indicator bulb’s sole purpose in life is to indicate a burned out bulb in the brake light assembly. If the warning light comes on when there is no fault with the bulbs, then there is a fault somewhere in the circuit that mimics a failed bulb.
If any other lights in the cluster come on when applying the brakes, there is a fault in the electrical system affecting the brake light circuit.

As an aside, perhaps it is time to buy a better crimping tool.

Thanks to you both, I'll find the manual and figure out where the relay is and where that wire runs as apparently I've had a fault this whole time based on what TexasKZ said.

Don't know where it is but if you follow the below and look for a unit with a three wire plug with these colours you should be "on the money"

 

Not 100% sure based on the manual, but think it may be inside the headlight:

 

Apparently it's definitely under the headlight, but bottom line if I just ignore it or pull the bulb it won't affect anything else, right? Will probably just order a switch and replace it but more curious if I can ride it in the meantime.

It's not the switch you are looking for it's the "bulb failure unit" and removing the bulb won't stop it potentially effecting the lighting circuit. The switch is presumably ok since you say the brake light was working

To be honest riding it with a faulty rear light is not the best idea as you risk getting "rear ended" however if you find and disconnect the right thing you may well find everything works as it should

Searched the manual and didn't find a reference to 'bulb failure unit' anywhere, only a 'brake light failure indicator switch'. Is that what you're talking about? Cause I'm thinking I'll just replace that. I don't really ever ride at night so I don't imagine it'll ever be a problem not having the running light going but still would rather it be working.

ThatYeti wrote:

Searched the manual and didn't find a reference to 'bulb failure unit' anywhere, only a 'brake light failure indicator switch'. Is that what you're talking about? Cause I'm thinking I'll just replace that. I don't really ever ride at night so I don't imagine it'll ever be a problem not having the running light going but still would rather it be working.

Yes that is it - why do you want to replace it when it won't work correctly anyway, just disconnect it and call it "done". I take it you don't have "inspections"  where you are, statutory lighting is a legal requirement here in the UK and Europe

Well I could follow the manual to test if it's the switch that's bad, but I really hate using the fucking multimeter with a passion. Thing doesn't make any sense to me and might as well be black magic as far as I'm concerned. Guess I could pull the headlight bucket and just unplug it, to your point but would rather have it working.

We do have inspections, but only initially on old bikes. After that you can probably do whatever you want, unless you get pulled over by an aggressive cop who's bored and just wants to ruin someone's day.

I'm not convinced it will ever work as intended with an LED light. I would suggest you learn to love your multimeter, trying to resolve electrical issues with "luck" and "guesswork" will normally have 1 of 4 outcomes

• You get lucky (not often)
• You drive yourself mad (often)
• You empty your wallet on parts you don't need (often)
• You get really unlucky and set your bike on fire (occasionally)

​​​​​​​Testing a 3 wire circuit like this should take around 20 mins if done correctly (but you need to learn to interpret what your meter is telling you)