I don't have the schematic for the 93 handy, but I'm guessing it's the old style, with the direction flasher and the hazard separate units.
You should have power in one leg of the flasher (with the flasher removed), with the ignition on. The other leg you can test for continuity to ground, when you turn the directional handle. This will tell you which end of the system is acting up.
The flasher itself has a heater coil and a bi-metal. The more bulbs on the flasher and the faster it flashes (you mentioned a trailer). There are universal flashers and there are specialty flashers, designed to be used with more bulbs.
A really bad mismatch can damage the flasher unit, pretty quick.
If you can get the parts guy to look in the book, it will say how many bulbs the flasher is designed for. You may need a HD flasher.
If you have the combination flasher, with the direction and hazard in one unit, this is another kettle of fish.
If you have the HD trailer towing package, there is a relay set in the back behind the spare tire panel. Though this shouldn't affect things much if it's failed, but it may have a short. There is a separate fuse for the trailer harness relay set, on my 88 it's behind the drivers side kick panel, it may be someplace else on yours.
Don't know if I've helped much, but didn't notice anybody else posting up.