Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Fig. 3 Coolant switch location. 4-135 & 4-153 engines:
PURPOSE
The coolant switch, Fig. 3, is located on the thermostat housing. It supplies a signal to the computer when the engine coolant temperature is below 150°F. This information is required to prevent a change in air fuel ratio until engine operating temperature is reached.