Try wiggling and cleaning the contacts on back of emergency flasher switch. Power to the turn signals goes through there and a bad contact at back of switch will snafu the turn signals. And maybe even leave the emerg. flashers working.

Also -
Pull clamshell covers off steering wheel + column. That's two screws each, top and bottom.

Remove turn signal switch (a couple more fat phillips head screws).
Clean up the contacts in the wire connector, and spray contact cleaner into the switch too. Work it back and forth a bunch.

Check ground screw on steering column, left side, just down from where the switch attaches. I think there are two wires to it, only for horn and the headlight dimmer - but you may as well make sure the ground is good while you're there.