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For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2004 🢒 Isuzu MD F-Series 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Air Delivery Improper

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

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

1

Did you review the HVAC operation and perform the necessary inspections?

--

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

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 in any of the speed positions?

--

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. Place the bi-level switch in the ON position.
  2. Observe the recirculation actuator.
  3. Place the recirculation switch in the ON and OFF positions.

Does the recirculation actuator operate?

--

Go to Step 6

Go to Air Recirculation Malfunction

6

Operate the mode switches through each mode position.

Does air flow from the correct air distribution outlets?

--

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

Go to Step 7

7

Inspect the mode door and the mode actuator for the following conditions:

    • A misaligned mode actuator.
        Refer to Mode Actuator Replacement .
    • Broken or binding linkages
    • A broken or binding mode door
    • An obstruction that prevents the mode door from operating within its full range of motion
    • Missing seals to the mode door
    • Misaligned seals to the mode door

Did you find and correct the condition?

--

Go to Step 21

Go to Step 8

8
  1. Observe the drive shaft of the mode actuator.
  2. Place the bi-level switch in the ON position.
  3. Place the defrost switch in the ON position.

Does the mode actuator shaft rotate?

--

Go to Step 15

Go to Step 9

9
  1. Turn OFF the ignition.
  2. Disconnect the mode actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from each mode door position signal circuit to a good ground

Do the voltages measure within the specified range?

6-8 V

Go to Step 11

Go to Step 10

10

Test the applicable mode door position signal circuit of the mode actuator for an open, short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

11

Test the ground circuit of the mode actuator for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 12

12

Test the mode door control A circuit and the mode door control B circuit of the mode actuator for an open, high resistance, short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 13

13
  1. Turn OFF the ignition.
  2. Connect the mode actuator.
  3. Disconnect the HVAC control module.
  4. Turn ON the ignition, with the engine OFF.
  5. Connect a 10 amp fused jumper wire between the mode door control A circuit of the mode actuator and battery positive voltage.
  6. Connect a 10 amp fused jumper wire between the mode door control B circuit of the mode actuator and a good ground.

Does the mode actuator shaft rotate?

--

Go to Step 18

Go to Step 14

14
  1. Connect a 10 amp fused jumper wire between the mode door control B circuit of the mode actuator and battery positive voltage.
  2. Connect a 10 amp fused jumper wire between the mode door control A circuit of the mode actuator and a good ground.

Does the mode actuator shaft rotate?

--

Go to Step 18

Go to Step 17

15
  1. Turn OFF the ignition.
  2. Disconnect the mode actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from each mode door position signal circuit and a good ground

Do the voltages measure within the specified range?

6-8 V

Go to Step 17

Go to Step 16

16

Test the applicable mode door position signal circuit of the mode actuator for an open, short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

17

Inspect for poor connections at the harness connector of the mode actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 19

18

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 20

19

Replace the mode actuator. Refer to Mode Actuator Replacement .

Did you complete the replacement?

--

Go to Step 21

--

20

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 21

--

21

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 7