GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Sonoma Pickup - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Air Delivery Improper

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for a blower motor that does not operate regardless of the desired blower motor speed.

    2.

  2. This step tests for a blower motor that operates, yet does not accurately respond to the desired blower motor speed.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: Air does not flow correctly from the air distribution outlets.

1

Did you perform the HVAC Diagnostic Starting Point in Heating, Ventilation and Air Conditioning?

Go to Step 2

Go to Diagnostic Starting Point - Heating, Ventilation and Air Conditioning

2
  1. Turn ON the ignition, with the engine OFF.
  2. Place the blower motor switch in the OFF position.

Is the blower motor OFF?

Go to Step 3

Go to Blower Motor Always On

3

Place the blower motor switch in each speed position.

Does the blower motor operate at all?

Go to Step 4

Go to Blower Motor Inoperative

4

Does the blower motor operate in each speed position?

Go to Step 5

Go to Blower Motor Malfunction

5

  1. Start the engine
  2. Place the blower motor switch in the maximum speed position.
  3. Place the mode switch in each position.

Is the airflow sufficient from the correct outlets in each mode?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Vacuum Control System Diagnostic