Where is the thermostat on 1994 ranger with 3.0 L V6 engine?

The thermostat on a 1994 Ford Ranger with a 3.0L V6 engine is located on the engine block, at the back of the engine, near the firewall. It's usually relatively low down and can be difficult to access without removing some components like the fan shroud or possibly even the upper radiator hose. You'll likely need a wrench and possibly some patience to get to it. A shop manual specific to your year and model will give you the most accurate location and instructions.