GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Safari - 4WD 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Heater Blower Controls System Check

Step

Action

Normal Result(s)

Abnormal Result(s)*

1
  1. Turn the ignition switch to the RUN position.
  2. Turn the mode switch to any position other than OFF.
  3. Move the blower speed selector switch to the following positions in the following order:
    4. 3.1. LOW
    3.2. M1
    3.3. M2
    3.4. HIGH
    3.5. LOW
  4. Move the temperature control knob from the extreme cold to the extreme hot position one step at a time.
  5. Turn the mode switch to the off position.
    • The blower motor speed will increase at each speed level when the blower speed selector switch moves toward the HIGH position.
    • The blower motor speed will decrease at each speed level as the switch moves toward the LOW position.
    • The blower motor stops when the mode switch is turned off.
    • The air should become warmer as the temperature control knob is turned toward to hot position.
    •  Blower Motor Always On
    •  Heating Insufficient

2

The following procedure only applies if the vehicle is equipped with rear HVAC controls.

  1. Turn the ignition switch to the RUN position.
  2. Move the temperature control knob to the extreme hot position.
  3. Move the rear blower speed selector switch to the following positions in the following order:
    4. 3.1. LOW
    3.2. MED
    3.3. HIGH
    3.4. LOW
    • The rear blower motor speed will increase at each speed level when the blower speed selector switch moves toward the HIGH position.
    • The blower motor speed will decrease at each speed level as the switch moves toward the LOW position.
    • The air should be warm if the vehicle is at operating temperature.

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