Is heated air same as manifold vacuum?

Coolant temperature switches were used for enabling/disabling EGR systems in many systems, and vacuum spark advance in some systems, but they were not used to control thermostatic air cleaners—by any automaker. That's because the relevant property is the temperature of air flowing into the carburetor, not the temperature of the engine coolant. Aside from some early Ford setups in the late '60s that used a wax pellet (like the one in the coolant thermostat) acting directly on the snorkel door, thermostatic air cleaner systems were all very similar regardless of brand. The AC thermo sensors GM used looked a little different to the Fram sensors used by Chrysler, Ford, and AMC, but they all worked and hooked up the same way.

Happy T-day to all.