new tail light brake light no working! what can i do?

wired up a new taillight. looks so good pictures later. but the brake light is not coming on. checked the connections and the wires are correctly matched up.

what else can i do to investigate the cause. One thing i did do during the installation was to try and rewire a usb port so i would only be usable when the start button is pressed and i messed up and put the positive to a negative terminal which caused a buzz noise and some worry on my part. but everything seemed okay afterwards except my new rear brake light will not come on, though the tail light works perfectly. any help would be so welcome/. from a dumb ass who never paid attention at school.

Have you checked the fuses, you may have shorted something out when you got the polarity wrong.

+1 check your fuses, they're behind the left gas tank shroud.

checked the fuses they all look in good condition.

I'd hook the stocker back up and see if it works. Maybe you got a bad aftermarket unit. If the stocker won't work you KNOW its an issue with your electrical system. Do you have a service manual? I can email you one if you pm me your address.

Use a test light or multimeter to check if you have power in the brake light wire close to the tail light, if you do the tail light is toast, if you don't you have a bad connection or wire.

forgive my ignorance. i just cant find the right youtube video. how do you do the test with a meter.

Put the meter on the 12 volt setting then do the following.

Stick the black/ground probe from the meter onto the negative battery post and stab the red/positive probe from the meter into the tail light wire or connector you want to check.

Since you are testing the brake light wire you will have to hold the brake pedal down or brake lever in to do this.

If you have power in the wire the meter will show 12-14 volts.

thanks for the simple and coherent advice. just blew a fuse yesterday (of course, with a different procedure).