GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Chevy Suburban - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Air Delivery System Check

Step

Action

Normal Result(s)

Abnormal Result(s)*

1
  1. Start the vehicle engine.
  2. Allow vehicle to reach operating temperature.
  3. Place the blower switch in the high position.
  4. Place the temperature knob in the full heat (red) position.
  5. Rotate the mode knob through each of the vent positions:
    6. • Defrost
    • Blend
    • Heater
    • Vent
    • Blower motor will operate at high speed.
    • Air temperature will be hot.
    • Air flow in the defrost position is through the defrost outlets.
    • Air flow in the blend position is through both defrost and heater outlets.
    • Air flow in the heater position is through the heater outlets.
    • Air flow in the vent position is through the A/C (vent) outlets.

Air flow does not change outlets: Mode Actuator Inoperative

2
  1. Place the temperature knob in the full cold (blue) position.
  2. Rotate the mode knob in each of the following positions:
    3. • Defrost
    • Blend
    • Heater
    • Vent
    • Blower motor will operate at high speed.
    • Air flow will change to the appropriate outlets.
    • Air temperature will be cooler.

Air temperature remains hot: Temperature Actuator Inoperative

3
  1. Press the A/C button.
  2. Place the temperature knob in the MAX position.
  3. Depress the A/C button and turn the temperature knob to medium/blend.
  4. Press the recirculation button.

An audible change in the blower will be noticed when in either MAX A/C or when the recirculation button is pressed.

No audible change in blower operation: Air Inlet Actuator Inoperative

4

If vehicle is equipped with an auxiliary HVAC unit perform the following steps:

  1. Place the front auxiliary HVAC control module blower switch in the high position.
  2. Place the mode knob in the lower position.
  3. Place the temperature knob in the full cold (blue) position.
    • Auxiliary blower motor will operate at high speed.
    • Air flow will be through the lower outlets of the auxiliary unit.
    • Air temperature will be cold.

5
  1. Place the front auxiliary HVAC control module mode knob in the overhead position.
  2. Place the temperature knob in the full hot (red) position.
    • Auxiliary blower motor will operate at high speed.
    • Air flow will be through the overhead outlets of the auxiliary unit.
    • Air temperature will be hot.

6

For vehicles with rear auxiliary HVAC control unit.

  1. Place the front auxiliary HVAC control module blower switch in the rear position.
  2. Place the rear auxiliary HVAC control module knobs in the following positions:
    3. • Blower switch in the high position.
    • Mode knob in the lower air delivery position.
    • Temperature knob in the full cold (blue) position.
    • Auxiliary blower motor will operate at high speed.
    • Air flow will be through the lower outlets of the auxiliary unit.
    • Air temperature will be cold.

7
  1. Place the rear auxiliary HVAC control module mode knob in the overhead air delivery position.
  2. Place the rear auxiliary HVAC control module temperature knob in the full hot (red) position.
  1. Auxiliary blower motor will operate at high speed.
  2. Air flow will be through the overhead outlets of the auxiliary unit.
  3. Air temperature will be hot.

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.