Of course, one always does a safety check of ones lights before leaving on a trip - right?! And though I could always get the turn lights to work eventually (I figured it was just a bit of corrosion on the connections), I recently realized that the lights were less than reliable while on the move - thus explaining why some angry drivers were honking at me when I blithely turned on my turn signals and changed lanes.
Careful cleaning of the connections, the bulbs, etc did not improve the reliablity of my turn signals. After calls to several RV maintenance places, I learned that it's hard to find anyone willing to troubleshoot electrical problems.
Fortunately, I found a little gizmo (for under $10!) on Amazon and was able to isolate the problem to my tow vehicle. From there it was a short trip to U-Haul to replace the converter and VOILA! - I have turn signals again!
I think this 7way circuit tester will find a permanent place in my trailer tool box!