See Figures 1, 2, 3 and 4
The rate of fuel atomization varies with the temperature of the air that the fuel is being mixed with, Cold air being drawn into the engine causes a denser and richer air/fuel mixture, inefficient fuel atomization, thus, more hydrocarbons in the exhaust gas. Hot air being drawn into the engine causes a leaner air/fuel mixture and more efficient atomization and combustion for less hydrocarbons in the exhaust gases.
The automatic temperature controlled air cleaner is designed so that the temperature of the ambient air being drawn into the engine is automatically controlled, to hold temperature, consequently, the fuel/air ratio at a constant rate for efficient fuel combustion.
A temperature sensing vacuum switch controls the vacuum applied to a vacuum motor, operating a valve in the intake snorkel of the air cleaner. When the engine is cold or the air being drawn into the engine is cold, the vacuum motor opens the valve, allowing air heated by the exhaust manifold to be drawn into the engine. As the engine warms up, the temperature sensing unit shuts off the vacuum applied to the vacuum motor which allows the valve to close, shutting off the heated air and allowing cooler, outside (under hood) air to be drawn into the engine.
INSPECTION & TESTING
When the air around the temperature sensor of the unit mounted inside the air cleaner housing reaches 100°F (38°C), the sensor should block the flow of vacuum to the air control valve vacuum motor. When the temperature around the temperature sensor is below 100°F (38°C), the sensor should allow vacuum to pass onto the air valve vacuum motor thus blocking off the air cleaner snorkel to under hood (unheated) air.
When the temperature around the sensor is above 118°F (48°C), the air control valve should be completely open to under hood air.
If the air cleaner fails to operate correctly, check for loose or broken vacuum hoses. If the hoses are not the cause, proceed to temperature and/or vacuum motor testing.Temperature Sensor Testing
See Figures 5 and 6
This procedure must be started when the engine is completely cold; if not use dry ice to cool the temperature sensor.
- Disconnect the vacuum hose from the vacuum motor.
- Using a vacuum T-type connector, connect a vacuum gauge in series with the vacuum motor. Reconnect the hose to the vacuum motor.
- Place a thermometer on the air cleaner housing, as close as possible to temperature sensor.
Start the engine and observe the vacuum gauge and air door position, at the following temperatures:
Temperature below 118°F (48°C) the vacuum gauge should read at least 4 inches of vacuum-Door fully open (fully raised)
If the door does not perform as specified, remove the vacuum supply hose from the temperature sensor. Verify that at least 4 inches of vacuum is available to the sensor.
If there an adequate vacuum supply to the temperature sensor, replace the ATC temperature sensor
- Disconnect the rubber hose from the vacuum motor.
- Connect a vacuum pump to the motor and apply vacuum.
The motor should hold vacuum indefinitely.
If the motor moves the air door and holds vacuum, the vacuum motor is operating properly.
Inspect the ATC system air door for sticking or binding.
If a problem is found with the door, repair as required.