Chrysler Full-Size Vans 1989-1998 Repair Guide

Heated Air Intake System

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OPERATION



See Figure 1

The heated air intake system is part of the air cleaner assembly. It controls the intake air temperature so the air/fuel mixture can be calibrated leaner when ambient temperatures are low. The system improves engine warm-up characteristics and minimizes icing problems in the cold.

When ambient air temperature is 15°F (8°C) or more above the control temperature, air flow is deflected through the outside air inlet. When the ambient temperature is below these values, warm intake air flow is taken from the heat stove on the exhaust manifold. The colder the temperature, the greater the amount of air taken through the stove. Air flow is controlled by a vacuum-operated door in the snorkel.

Modulation of induction air temperature is controlled by intake manifold vacuum, a temperature sensor and vacuum diaphragm. Temperature modulation only occurs at road load throttle positions or when the intake manifold vacuum is above the operating vacuum of the diaphragm.

Improper operation of the heated air intake system will cause driveability problems and high emissions. Make sure all vacuum hoses and the stove to the air cleaner flexible connector are properly attached and in good condition. With a cold engine and ambient temperature below 110°F (44°C), the heat control door in the snorkel should be in the UP position. With the engine warmed up and running, or when the intake air temperature goes above 130°F (54°C), the control door should be in the DOWN position.



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the heated air intake system-3.9L engine

TESTING



System Test

See Figure 2

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Use a hand held vacuum pump to apply 25 in. Hg to the diaphragm.
  6.  
  7. The diaphragm should not bleed down more than 10 in. Hg in 5 minutes.
  8.  
  9. The door should not lift off the bottom of the snorkel with less than 2 in. Hg of vacuum applied.
  10.  
  11. The door should be in the full UP position with 4 in. Hg applied.
  12.  
  13. If the vacuum diaphragm does not perform as described, replace it. If it operates normally, proceed to the next step.
  14.  
  15. Remove the air cleaner from the engine. If the temperature of the air cleaner is not 112°F (45°C) or less, allow it to cool.
  16.  
  17. Apply 20 inches of vacuum to the temperature sensor, if the air door is not in the closed position, the diaphragm is suspect. If the vacuum diaphragm performs correctly, but the proper temperature is not maintained, replace the temperature sensor.
  18.  
  19. Install the engine cover.
  20.  
  21. Connect the negative battery cable.
  22.  



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Fig. Fig. 2: Use a hand held vacuum pump to test the air cleaner vacuum diaphragm

REMOVAL & INSTALLATION



Vacuum Diaphragm

See Figures 3 and 4

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the air cleaner from the vehicle.
  6.  
  7. Disconnect the vacuum hose from the blend door diaphragm.
  8.  
  9. Drill out the diaphragm mounting rivet. Tip the diaphragm slightly forward to disengage the lock. When the diaphragm is free, slide the complete assembly to one side to disengage the operating rod from the blend air door.
  10.  
  11. With the diaphragm removed from the air cleaner, check the blend air door for freedom of travel. When the door is raised, it should fall freely. Adjust as necessary.
  12.  

To install:
  1. Place the diaphragm in position on the air cleaner and engage the rod to the blend air door. Mount the diaphragm with a rivet.
  2.  
  3. Apply 4 inches of vacuum to the diaphragm. The control door should operate freely.
  4.  
  5. Install the air cleaner, start the engine and check the blend air door operation.
  6.  
  7. Install the engine cover.
  8.  
  9. Disconnect the negative battery cable.
  10.  



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Fig. Fig. 3: Drill out the rivet that retains the vacuum diaphragm



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Fig. Fig. 4: Lift out and remove the vacuum diaphragm assembly

Heated Air Temperature Sensor

See Figure 5

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the air cleaner assembly from the vehicle.
  6.  
  7. Remove and discard the sensor mounting clip. Remove the sensor.
  8.  
  9. Position the mounting gasket on the sensor. Install the sensor in position on the air cleaner.
  10.  
  11. Support the sensor and slide the new retainer into position. Make sure the sensor is secure and in the proper position with the mounting gasket to ensure a tight air seal.
  12.  
  13. Install the air cleaner assembly.
  14.  
  15. Install the engine cover.
  16.  
  17. Connect the negative battery cable.
  18.  



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Fig. Fig. 5: Slide off the retaining clip to remove the air temperature sensor

 
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