Len,
OK, I tried it without the 100k resistor and pulldowns, but with the 470 ohm resistors parallel to the LEDs. With that configuration, connecting only the brake input to 6V would light the brake LEDs but not the flasher LEDs. However, replacing the 100k resistor did the trick. I changed the 100k resistor to 22k and it worked perfectly.
This does not make any sense. How can 100k resistors work and 470 Ohm resistors not work?
What LEDs are you referring to?
What I mean is the LEDs that are in place of the lamp I called "Front Lamp" in my drawing. This and the "Centre Lamp" need to have a 470 Ohm resistors in parallel with them.
I think I'm going to cram for a while with my books and calculator to try to figure out exactly what's going on here, what the current paths are, and maybe order some real 3906s to work with instead of these so-called "similar" PNPs I've got here.
The transistor type should make no difference. Virtually any PNP should do.
Thanks again,
Torben