The thermostat housing on a 2004 Chrysler Sebring Convertible (assuming the 2.4L engine, as that was the most common) is located at the
front of the engine, on the passenger side. It's usually fairly low down, near where the upper radiator hose connects to the engine. You'll likely need to look closely and possibly remove some shrouding or plastic covers to get a good view.
Important Note: Accessing it will likely require some mechanical aptitude and possibly special tools. If you're not comfortable working on your car's engine, it's best to take it to a qualified mechanic.
