Classic/Antique Car Repair: Thermostatic vacuum switch, vacuum switch, vacuum advance

Question
1970 Olds delta 88 455. How can I tell if the thermostatic vacuum switch is operational, and if so, is it really needed? I recently got the air conditioner working, and since have experienced overheating, the vacuum switch has three tubing/hose outlets with nothing hooked to them, I do have a shop manual for this car, but it doesn't state how to check the switch. thanks

Answer
Kevin, the thermostatic vacuum switch that you have is an attempt by the car makers to meet emissions standards. Originally the switch interrupted the vacuum to the distributor vacuum advance and advanced or retarded ignition timing relative to engine temperature. This did reduce tail pipe emissions but under certain conditions reduced engines power and also increased fuel consumption. Most of these switches were soon bypassed in an attempt to get the engine to run better with better fuel economy. It does not control engine temperature. If you started having engine overheating after getting the air conditioning working you might want to check the fan clutch on the cooling fan and make sure that the radiator is not partially plugged. Remember that the heat that you remove from inside the car is added to the air flow coming into the radiator.
Brad