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Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon XL - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Air Delivery Improper - Auxiliary

Air Delivery Improper - Auxiliary W/O Sunroof

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step tests for auxiliary blower motor that does not operate from the front auxiliary HVAC control assembly regardless of the desired blower motor speed.

    2.

  2. This step tests for a auxiliary blower motor that operates, yet does not accurately respond to the desired blower motor speed from the front auxiliary HVAC control assembly.

    3.

  3. This step tests for auxiliary blower motor that does not operate from the rear auxiliary HVAC control assembly regardless of the desired blower motor speed.

    4.

  4. This step tests for a auxiliary blower motor that operates, yet does not accurately respond to the desired blower motor speed from the rear auxiliary HVAC control assembly.

    5.

  5. This step tests for an inoperative auxiliary mode actuator in one mode position(s) or in the wrong mode position(s) from either auxiliary HVAC control assemblies.

    6.

  6. This step tests for an incorrectly installed auxiliary mode actuator, damaged attaching linkage(s). Any mechanical repairs will not require the auxiliary mode actuator to be replaced.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: Air does not flow correctly from the auxiliary 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 IP HVAC control assembly to the rear position.
  3. Place the front auxiliary HVAC control assembly blower control in the OFF position.
  4. Place the rear auxiliary HVAC control assembly blower control in the OFF position.

Is the auxiliary blower motor OFF?

--

Go to Step 3

Go to Auxiliary Blower Motor Always On

3

Place the front auxiliary control assembly blower control in each mode position.

Does the auxiliary blower motor operate at all?

--

Go to Step 4

Go to Auxiliary Blower Motor Inoperative

4

Does the auxiliary blower motor operate correctly for each mode position?

--

Go to Step 5

Go to Auxiliary Blower Motor Malfunction

5

  1. Place the front auxiliary HVAC control assembly blower control in the rear control position.
  2. Place the rear auxiliary HVAC control assembly blower control in each mode position.

Does the auxiliary blower motor operate at all?

--

Go to Step 6

Go to Auxiliary Blower Motor Inoperative

6

Does the auxiliary blower motor operate correctly for each mode position?

--

Go to Step 7

Go to Auxiliary Blower Motor Malfunction

7

Do either auxiliary HVAC control assemblies operate correctly in any mode position?

--

Go to Step 8

Go to Step 23

8
  1. Place the front auxiliary HVAC control assembly blower control in the high position.
  2. Place the front auxiliary HVAC control assembly mode control in each mode position.

Does the auxiliary mode actuator operate correctly for each mode position?

--

Go to Step 9

Go to Step 10

9
  1. Place the front auxiliary HVAC control assembly blower control in the rear control position.
  2. Place the rear auxiliary HVAC control assembly blower control in the high position.
  3. Place the rear auxiliary HVAC control assembly mode control in each mode position.

Does the auxiliary mode actuator operate correctly for each mode position?

--

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

Go to Step 12

10

Test the ignition 3 voltage circuit of the front auxiliary HVAC control assembly for an open, or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 11

11

Test the ignition 3 voltage circuit of the HVAC control processor - auxiliary for an open, or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 12

12

Test the ignition 3 voltage circuit of the auxiliary mode actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 13

13

Test the ground circuit of the front auxiliary HVAC control assembly for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 14

14

Test the ground circuit of the HVAC control processor - auxiliary for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 15

15

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

Did you find and correct the condition?

--

Go to Step 35

Go to Step 16

16
  1. Measure the voltage from the mode signal auxiliary front circuit at the rear HVAC programer to a good ground.
  2. Place the front auxiliary HVAC control assembly mode control in each mode position.

Does the voltage measure less than the specified value in each mode position?

12 V

Go to Step 17

Go to Step 20

17

Does the voltage measure near the specified value in each mode position?

0 V

Go to Step 21

Go to Step 26

18
  1. Place the front auxiliary HVAC control assembly blower control in the rear control position.
  2. Measure the voltage from the mode signal auxiliary rear circuit at the rear HVAC programer to a good ground.
  3. Place the rear auxiliary HVAC control assembly mode control in each mode position.

Does the voltage measure less than the specified value in each mode position?

12 V

Go to Step 19

Go to Step 22

19

Does the voltage measure near the specified value in each mode position?

0 V

Go to Step 23

Go to Step 27

20

Test the mode signal auxiliary front circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 26

21

Test the mode signal auxiliary front circuit for an open, a high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 26

22

Test the mode signal auxiliary rear circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 27

23

Test the mode signal auxiliary rear circuit for an open, a high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 27

24

Test the mode door control auxiliary circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 25

25

Test the mode door control auxiliary circuit for an open, a high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 28

26

Inspect for poor connections at the harness connector of the front auxiliary HVAC control assembly. 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 35

Go to Step 31

27

Inspect for poor connections at the harness connector of the rear auxiliary HVAC control assembly. 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 35

Go to Step 32

28

Inspect for poor connections at the harness connector of the HVAC control processor - auxiliary. 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 35

Go to Step 33

29

Inspect for poor connections at the harness connector of the auxiliary 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 35

Go to Step 30

30

  1. Test the auxiliary mode actuator, door and any attaching linkage for any binding.
  2. Inspect the ductwork for any debris that would prevent air to flow through the ductwork.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 34

31

Replace the front auxiliary HVAC control assembly . Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

--

Go to Step 35

--

32

Replace the HVAC control assembly - auxiliary rear. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

--

Go to Step 35

--

33

Replace the HVAC control processor - auxiliary . Refer to Auxiliary HVAC Control Processor Replacement .

Did you complete the replacement?

--

Go to Step 35

--

34

Replace the mode actuator-auxiliary . Refer to Auxiliary Mode Valve Actuator Replacement .

Did you complete the replacement?

--

Go to Step 35

--

35

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2

Air Delivery Improper - Auxiliary W/Sunroof

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

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

    2.

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

    3.

  3. This step tests for an inoperative auxiliary mode actuator in one mode position(s) or in the wrong mode position(s).

    4.

  4. The front auxiliary HVAC control assembly mode switch control circuit will normally vary between 0-12 volts.

    5.

  5. An incorrectly installed auxiliary mode actuator, damaged attaching linkage(s). Any mechanical repairs will not require the mode actuator-auxiliary to be replaced.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: Air does not flow correctly from the auxiliary 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 IP HVAC control assembly to the rear position.
  3. Place the front auxiliary HVAC control assembly blower control in the OFF position.

Is the auxiliary blower motor OFF?

--

Go to Step 3

Go to Auxiliary Blower Motor Always On

3

Place the front auxiliary HVAC control assembly blower control in each mode position.

Does the auxiliary blower motor operate at all?

--

Go to Step 4

Go to Auxiliary Blower Motor Inoperative

4

Does the auxiliary blower motor operate correctly for each mode position?

--

Go to Step 5

Go to Auxiliary Blower Motor Malfunction

5

  1. Place the front auxiliary HVAC control assembly blower control in the high position.
  2. Place the front auxiliary HVAC control assembly mode control in each mode position.

Does the auxiliary mode actuator operate correctly for each mode position?

--

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

Go to Step 6

6

Test the ignition 3 voltage circuit of the front auxiliary HVAC control assembly for an open, a high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 7

7

Test the ground circuit of the front auxiliary HVAC control assembly for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 8

8

Test the ignition 3 voltage circuit of the auxiliary mode actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 9

9

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

Did you find and correct the condition?

--

Go to Step 19

Go to Step 10

10

  1. Measure the voltage from the auxiliary mode door control circuit at the auxiliary mode actuator to a good ground.
  2. Place the front auxiliary HVAC control assembly mode control in each mode position.

Does the voltage measure less than the specified value in each mode position?

12 V

Go to Step 11

Go to Step 12

11

Does the voltage measure near the specified value in each mode position?

0 V

Go to Step 13

Go to Step 15

12

Test the auxiliary mode door control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 14

13

Test the auxiliary mode door control circuit for an open, a high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 14

14

Inspect for poor connections at the harness connector of the front auxiliary HVAC control assembly. 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 19

Go to Step 17

15

Inspect for poor connections at the harness connector of the auxiliary 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 19

Go to Step 16

16

  1. Test the auxiliary mode actuator, door and any attaching linkage for any binding.
  2. Inspect the ductwork for any debris that would prevent air to flow through the ductwork.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 18

17

Replace the front auxiliary HVAC control assembly . Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

--

Go to Step 19

--

18

Replace the mode actuator- auxiliary . Refer to Auxiliary Mode Valve Actuator Replacement .

Did you complete the replacement?

--

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2