Where is the thermostat on a 93 Ford Ranger 4.0 v-6?

The thermostat on a 1993 Ford Ranger 4.0L V6 is located on the engine, at the back of the engine, near the firewall. It's usually part of the engine's housing, not easily visible without some disassembly or removal of parts. You'll likely need to remove some components to access it. A repair manual specific to your year and engine will provide the most accurate location and instructions for replacement.