The switch for the backup light switch for an automatic transmission is located on the transmission where the shifting cable enters the transmission (The side of the transmission closest to the radiator),how about for the manual trans mission models?
It is located at the engine end of the upper radiator hose. Take the thermostat housing off. When replacing the thermostat make sure the spring goes toward the engine. It is not the upper radiator hose...it is the lower one..