Hi Chris:
Are you talking about the turn signals in your rear lights? I had a similar problem in my BT7, and found that the current wires into each of the rear lamps were reversed. To check this, turn your ignition key on, then turn on your headlights, and engage either turn signal. Look real closely at the rear lamp that you engaged. Is the turn signal truly not flashing, or is it just flashing very faintly? If it is the latter (as it was in my case), the headlamp circuit was running through the brighter filament of the bulb, and the stop/turn signal circuit was going through the dimmer filament. The brighter filament of the bulb was almost completely drowning out the flashing going on through the dimmer filament. Switching the current wires at the lamp remedied the situation.
When my headlamps were turned off, the flashing of the turn signal (through the dimmer filament) was visible, as it was not being drowned out, and appears to be working.
I remedied this a couple of years ago, and everything has worked since. I also recall that before the repair, and whether or not the headlamps were on, that when I engaged either turn signal, that the green flasher indicator on the dash would blink about three times and then go out. After the repair, when either turn signal is engaged, the indicator flashes until canceled.
I hope this helps!
Jerry