89 Katana 750 tail light short

I am having an issue with the lights at the back of my 89 750 Katana. Without warning, my tail light and license late light died. When I apply the brake light, the tail light circuit would light Long story short, here is where I am now:

When I plug in the license plate light, it shorts the system. When I plug in an accessory light I have, or I use my test light, it works normally.

When I plug in my tail light/brake light, it shorts the system. When I plug in another dual filament light, it shorts out the system. When I plug in two separate lights to the brake light, tail light harness and have a single filament light, other than the factory light, plugged into the license plate light, the entire system works fine.

Why are dual filament lights shorting my tail light/ brake light, but separate single filaments are ok. Also, I jumped ground straight to negative on the battery and it makes no difference.

Non of this makes sense. It is totally illogical. Even the folks on the Katana board are stumped.

Please help me.

When I at attach any dual filament setup, it craps out. When I mount a multi-functon LED strip, the electrics worth perfectly.

It sounds like you have a short to ground on the hot side of the tail/license light circuit. That is why the tail light lights up when the brake light is on. Power to the brake light is finding another way to ground through the tail light. It is likely that some insulation has worn off one of the leads going to the tail or license lights probably at or inside the lamp socket. A little heat shrink tubing would cure this.

Yup, found it. It is in the socket. Once I hooked up my other dual filament light correctly :-[ all worked well. New (used) OEM socket on the way.

TripleKing said:

Yup, found it. It is in the socket. Once I hooked up my other dual filament light correctly :-[ all worked well. New (used) OEM socket on the way.

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Soldered a new ground wire into the current tail light plug and everything works There was also a secondary problem with a bad connection in the license plate light. I think this cropped up after I moved wires, but this is fixed. I have a new tail light socket on the way. Meanwhile, the old Kat is up and running, very well I might add.