Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Automatic Temperature Controlled (ATC) Air Cleaner

Print

OPERATION



See Figures 1, 2, 3 and 4



Click image to see an enlarged view

Fig. Fig. 1: Air temperature control system operation-cold engine



Click image to see an enlarged view

Fig. Fig. 2: Air temperature control system operation-hot engine



Click image to see an enlarged view

Fig. Fig. 3: Air temperature control system component locations



Click image to see an enlarged view

Fig. Fig. 4: Air temperature control system component identification

Carbureted and Throttle Body Injected Engines

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



System Inspection

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



Click image to see an enlarged view

Fig. Fig. 5: Connect a vacuum gauge in series with this vacuum hose



Click image to see an enlarged view

Fig. Fig. 6: If using this method to check temperature sensor operation, use extreme care when heating the sensor. Damage to the sensor can occur if it is exposed to extreme heat

This procedure must be started when the engine is completely cold; if not use dry ice to cool the temperature sensor.

  1. Disconnect the vacuum hose from the vacuum motor.
  2.  
  3. Using a vacuum T-type connector, connect a vacuum gauge in series with the vacuum motor. Reconnect the hose to the vacuum motor.
  4.  
  5. Place a thermometer on the air cleaner housing, as close as possible to temperature sensor.
  6.  
  7. 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)
     
    Temperature between 100-118°F (38-48°C) the vacuum gauge should read approximately 4 inches of vacuum-Door 1 / 2 open (partially raised)
     
    Temperature above 100°F (38°C) the vacuum gauge should read approximately 2 inches of vacuum-Door fully closed (completely down)
     

  8.  
  9. 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
     
    If there is not an adequate vacuum supply to the temperature sensor, check and repair vacuum source problem
     

  10.  

Vacuum Motor Testing
  1. Disconnect the rubber hose from the vacuum motor.
  2.  
  3. Connect a vacuum pump to the motor and apply vacuum.
  4.  
  5. The motor should hold vacuum indefinitely.

    If the motor moves the air door and holds vacuum, the vacuum motor is operating properly.
     
    If the motor holds vacuum, but does not move, proceed to the next step.
     
    If the motor does not hold vacuum, replace the vacuum motor.
     

  6.  
  7. Inspect the ATC system air door for sticking or binding.

    If a problem is found with the door, repair as required.
     
    If no problems are found with the door, replace the vacuum motor.
     

  8.  

 
label.common.footer.alt.autozoneLogo