See Figure 1
This system is designed to stabilize the temperature of air going to the carburetors in order to permit smooth operation with leaner fuel/air mixtures. It incorporates a temperature sensor which feeds a vacuum motor varying the amount of vacuum according to the temperature of the air in the air cleaner. The vacuum motor controls an air door which in turn controls the amount of air to pass over the exhaust manifold on its way to the air cleaner.
The ATC air cleaner is equipped only on carbureted engines.
- Allow the engine to cool until the engine compartment is below 86°F (30°C). Make sure that the air door is open.
- Start the engine and operate it at idle. If the air door closes right away, it and the vacuum motor are in good condition.
- Watch the air door to ensure that it opens gradually. In hot weather, it will eventually open all the way; in cold weather, it will open only slightly.
- If there is doubt about the operation of the system, tape a small thermometer to the inside of the air cleaner cover, as close as possible to the sensor. Then operate the engine until the thermometer has had time to reach a stable reading. Finally, open the air cleaner and read the thermometer. It should read between 100-130°F (38-55°C).
- If the system is faulty, the vacuum motor may be tested by removing its vacuum supply hose from the temperature sensor and connecting it directly to the manifold. If the valve closes with the engine operating at idle speed, the problem must be in the temperature sensor or the hoses.