Okay, the problem is solved for the turn signals. As it turned out, the fuse was loose in the fuse box, and was not making good contact. I removed the fuse box, took it apart (it's not really designed to come apart, and it was tricky getting it back together), and put everything back together.
The heater/ac fan may have also been running off of that same circuit. I'm not certain, so I need to do some more investigation about that. But for now, everything is working fine.
