Hyundai Repair: flasher/blinker problem, left turn signal, tail lamps

Question
The left turn signal on my 2006 Sonata GLS started to blink rapidly, which I believe means that the flasher is going out.  So I ordered a new one, switched it, and no improvement.  Drove it home, then drove another errand.  Now the blinker is working fine.  Got to my destination, when I left, the blinker was back to rapid flashing.  Any ideas?

Answer
This issue is typically caused by a burned out turn signal bulb (or an open circuit in the wiring to that bulb).  Start by turning on the hazard lamps and check the exterior lamps as well as the indicators in the dash.  Expect that you'll find one of the left side lamps not flashing.  If so, that bulb is likely burned out.

If all the lamps appear to be flashing, then be a little more critical of the brightness of the lamps.  If one (most likely the left front) is dimmer than the others it is likely to have an open in the ground circuit.  If you see nothing abnormal using this method, you could recheck again after turning on the tail lamps and rechecking the front bulbs.