My left turn signal makes all 3 lights on the back of my 99 wrangler. then when you hit the brake while the left turn signal is on, all 3 rear lights just light up solid.

check that all your bulbs are correct and are making contact. this commonly happens when a wrong bulb is installed in a socket. the other reason this happens is a bad ground, and one bulb uses another as a ground path. I would start at the rear left light and check that everything is good there, then move on to the front. 99 percent of these kinds of problems are at the lights themselves.

Short between the rear indicator light and the brake lights.

see all indicator bulbs it only happens when one or more of the signal bulb fails to work

i would say you need to replace the flasher fuse for the turn signals.is you radio aftermarket

check the rear lights on the right side it sounds like u have
rusty sochets or water seeping in side the lens.

gl G

Did the new lens come with new sockets? If not damage may have occured there that you cant see. only other possibilty is wiring damage in the rear that may be hard to see. The condition you describe is simple "backfeeding" if you look hard enough youll either find bad sockets or damaged wires close to the lens that took the hit. Hope this helped. Thanks

You have a broken wire to the turn/brake light portion of the light as they use the same wire. Or where the plug goes into the light assy could be bad. Torsion mount lights are horrible and you should think about replacing with a universal light that you can wire direct.

TURN SIGNALS WILL FEED BACK THROUGH THE TURN SIGNAL SWITCH.THEY ARE INDEPENDENT OUT SIDE ON THE CAR BUT NOT IN THE SIGNAL SWITCH.REPLACE THE SIGNAL SWITCH

could be both unrelated issues at the same time

worn indicator stalk
faulty relays

adjust or test the brake pedal stop light switch

Looks as though you have earthing problems.
I would make sure that the earthing is O.K on flasher and brake.
You would then find your symptom disappear.

Hope that sorts it.