Thermostatic Vacuum Switch

On 3.1L, a wax pellet-type thermostatic vacuum switch is installed in the engine coolant passage in the intake manifold. Two vacuum fittings on switch connect to charcoal canister and the TBI unit. When coolant temperature is less than 115°F (46°C), switch will be closed, preventing purging of canister. When coolant temperature increases to greater than 115°F (46°C), switch will open, allowing purging of canister.