OK, according to my schematic for the '93 chevy, there is no fuse associated with the power lock system. There is one 30 amp Circuit Breaker that protects the system. The circuit breaker is located on the fuse block. When looking at the F/B, the C/B is at the right side, 2nd port from the bottom (just above the 5A "Crank" fuse).
The easiest way to check your lock system would be to exchange that C/B with the C/B directly above it (in the fuse box. That other C/B that is above it, is for the power windows). If the locks work after swapping the C/B's, then the original circuit breaker (for the lock system) is bad. Replace it with the same type/rating circuit breaker.
If that doesn't work, you need to start checking the wiring. You can start by checking the larger sized Orange w/black striped wire. This wire is the one that supplies power to the lock circuit. You can't see it, but that Org/Blk wire comes out from the back of the fuse box (in a harness/bundle) and goes to the Convenience Center (located under the dash, on the left side.) There are no fuses in the Convenience center, just wires that connect to it via a plastic connector. You can see the color of the wires that go into the connector there. Ensure that the plastic connector did not get inadvertently yanked out, vibrated out or simply has corrosion on the metal contacts. The wire is still the larger Org/Blk wire (Circuit #60).
Using a test light or a Volt meter, check for power at the Org/Blk wire at the Convenience center. This wire is HOT at all times. Also, at the Convenience center, check the Gound wire for the LOCK ciruit. It is circuit #150 and connects there at the lower right side of the C/C.
From the Convenience center, the Org/Blk wire is spliced and goes to each of your LOCK/UNLOCK switches on your door.
The Ground wire for the LOCK/UNLOCK circuit runs from the Convenience center to the Driver's side LOCK/UNLOCK switch only. This supplies both left and right side switches with an appropriate ground wire due to its associated wiring design.
Do the above checks, and if you still can't find the problem, let me know I will try to help you figure it out further (may be the driver's side switch is bad).
I attached the wiring diagram below so you can test for power/ground
Monday, November 2nd, 2009 AT 8:29 AM