I am having a strange problem with my turn lights. 
- With the headlights off, turn lights are working fine (i.e. blinks normally)
- With the headlights on, the turn light works fine to the right, but not to the left. 
  Left turnlights just stays on without blinking.
- Emergency/Hazard links blink OK, regardless of the headlights being on or not.

 This is a 1987 Syncro Westy.
I haven't taken anything apart yet, but am curious if anybody has any ideas or has run into a similar situation. Archive search didn't turn up anything quite similar to this problem.

--Thomas