You have a ground issue. More than likely it is not grounded properly. These can be very, very, hard to find. Been there and done that. I can only tell you to check all ground connections at the taillight assembly.
signal lights not working.
Replace the front and rear turn signal bulb....the elements inside are touching and backfeeding the system
Either hand signal or check and replace your fuses and turn signal bulbs.
When the signal lights are not working on a car, there are a couple of things that could be going on. One could be that the bulb needs to be replaced. The other possibility is that the signal relay needs to be replaced.
It's the turn signal indicator-located behind the hazard lights.You have to take it out and replace it.
Trun signal lights do not come on at all not on dash or outside
bad fuse or hazard switch
Signal lights staying on withot flashing indicates either front or rear signal bulb not working on the Audi
Turn left indicator signal flashes rapidly when I use indicator, bulbs ok, no lights working
Probably the flasher unit needs to be replaced. This is an electronic switch which usually mounts underneath the dashboard.
turn signal switch needs replaced!
It sounds like you have a turn signal bulb out probably the left rear.