Thermostatic Air Cleaner

When air temperature is low, sensor valve at bottom of air cleaner body is in closed position. This allows a great deal of vacuum to be applied to vacuum motor and mixing door is fully opened. This admits heated air to the system. When air temperature increases, sensor valve opens and reduces vacuum applied to vacuum motor. This in turn causes mixing door to admit cool air. When manifold vacuum is greater than 3.94 in Hg and exhaust manifold is heated, warm air is drawn into engine.