Several comments:

-383 was an ambiguous number. I thought it was in reference to the Sunpak 383 (similar to the Vivitar 283/285). I now realize that the "383" flash in question is a Vivitar. Please ignore the comments about Sunpak.

-The Vivitar 385HV is not a TTL flash. It's only auto sensor/thyristor. Just like the 285. In theory it (or any auto thyristor flash) should fire in auto mode regardless of ambient light level. There are many situations (not just fill flash) in which one might wish to use flash in high ambient light levels. Often, auto sensor flashes don't put out enough light in bright conditions due to being overwhelmed by the ambient light. But they do (or should) fire no matter what. I've never experienced one that wouldn't fire at all. Again, please remove the flash from the camera and fire it using the test button in auto mode to determine the issue. If it actually does fire, but at a low level, that is expected behavior. To compensate, a smaller auto f/stop power level should be set. It may be impossible to use for main light under bright conditions. But it should at the very least work for fill.

Does anyone else have the Vivitar 385HV and can test it in auto sensor mode in bright light?