Tail light issues

 Ok looking for some advice or ideas running out of ideas. Putting bike back together and when I apply the brake the tail light dims instead of getting brighter. Checked all the fuses and ground all seems good about to deep clean connections. I did change out factory turn signals that had running lights in them they are led would that cause some issues was happy to see that they blink normally and didn't have to change blinker relays. The bike is a 81 kz750h ltd and thanks for any help ahead of time. 

I had a problem with my 40 year old tail light. Had me pulling my hair out. Turned out to be a aluminum rivet for the ground wire. Cleaned it up and re-riveted it now it works as it had the last 40+ years.
Steve

Thank you ill have to check that too but think its the brake light is on all the time and when i apply the brake it shuts it off or grounds it out just did some simple testing and figured out that both wires running to the tail light are hot untill brake level is pressed so now i guess im chassing that down because im pretty sure thats not right. 

There should be three wires running to the tail light.
One power for the running light, one power for the brake light (power coming on when either brake is used), and a ground wire.

I put some LED signals up front, and needed an LED specific relay, as the aftermarket Electronic signal relay did not allow the signals to flash correctly.
FL2-RED LED Bulb Electronic Flasher | Super Bright LEDs

Well do you ever feel like a complete idiot? Yeah im a idiot after about a day of chasing this and looking at a ton ot things you come to find out everything is working right. So still in the process of putting everything back on the bike and dont have the front brake lever in which is causing the brake light to be on. Also found out that the 2 hours i spent last night wiring up the tail and adding a new wire to the harness for the tail that i hooked it up to the brake light and not the running light wire. Guess its true 1 step forward 2 steps back lol. I want to thank you guys for all the good suggestions and help. 

One thing also to remember about LED lights, the are polarity specific, unlike incandescent that could care less. I have had good luck (2years) with the same flasher relay rstnick posted. Oh and yes they are polarity specific also. Real simple though if they don’t work just switch the wires and your on the road. I updated all the lighting to LED on my ‘78 1000 LTD.