Chrysler Full-Size Trucks 1989-1996 Repair Guide

Heated Air Intake System

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See Figures 1, 2, 3 and 4

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 cold weather.



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Fig. Fig. 1: Components of the heated air intake system as found on the 2.5L engine



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Fig. Fig. 2: Exploded view of the heated air intake system-V6 engine

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.



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Fig. Fig. 3: Air cleaner components utilized by the heated air system-2.5L engine



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Fig. Fig. 4: Use a hand-held vacuum pump to test the air cleaner vacuum diaphragm

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.

TESTING



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.

To test the door control diaphragm, use a hand vacuum pump to apply 25 in. Hg (84.5 kPa). The diaphragm should not bleed down more than 10 in. Hg (34 kPa) in 5 minutes. The door should not lift off the bottom of the snorkel with less than 2 in. Hg (6.75 kPa) of vacuum applied. The door should be in the full UP position with 4 in. Hg (13.5 kPa) applied. If the vacuum diaphragm does not perform as described, replace it.

REMOVAL & INSTALLATION



Vacuum Diaphragm

See Figures 5, 6 and 7

  1. Remove the air cleaner from the vehicle.
  2.  
  3. Disconnect the vacuum hose from the blend door diaphragm.
  4.  
  5. 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.
  6.  



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Fig. Fig. 5: Drill out and remove the rivet

  1. 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.
  2.  



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Fig. Fig. 6: Disconnect the vacuum hose, then drill out the rivet to replace the heated inlet air vacuum diaphragm

  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.  



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Fig. Fig. 7: Lift out and remove the vacuum diaphragm assembly

  1. Apply 4 in. Hg (13.5 kPa) of vacuum to the diaphragm. The control door should operate freely.
  2.  
  3. Install the air cleaner, start the engine and check the blend air door operation.
  4.  

Heated Air Temperature Sensor

See Figure 8

  1. Remove the air cleaner from the vehicle.
  2.  
  3. Remove and discard the sensor mounting clip. Remove the sensor.
  4.  
  5. Position the mounting gasket on the sensor. Install the sensor in position on the air cleaner.
  6.  



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Fig. Fig. 8: Remove the air temperature sensor retaining clip and remove the sensor

  1. 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.
  2.  

 
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