Schematic Reference: HVAC Schematics

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

1

Did you perform the HVAC Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

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

Is the blower motor OFF?

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Go to Step 3

Go to Blower Motor Always On

Place the blower control in each speed position.

Does the blower motor operate in any of the speed positions?

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Go to Step 4

Go to Blower Motor Inoperative

Does the blower motor operate at the desired speeds?

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Go to Step 5

Go to Blower Motor Malfunction

1. Start the engine
2. Place the blower control in the maximum speed position.
3. Place the mode control in the vent position.
4. Place the recirculation switch in the ON and OFF positions.

Does the recirculation door move from the recirculation position to the ambient air position?

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Go to Step 6

Go to Air Recirculation Malfunction

Place the mode switch in each position.

Does the air flow from the correct air distribution outlet(s) for each mode selected?

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Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 7

7

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, command each vacuum solenoid ON and OFF.

Does each vacuum solenoid turn ON and OFF with each command?

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Go to Vacuum Control System Diagnostic

Go to Step 8

1. Turn OFF the ignition.
2. Disconnect the vacuum control assembly.
3. Turn ON the ignition, with the engine OFF.
4. Probe the vacuum control assembly supply voltage circuit of the vacuum control assembly with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

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Go to Step 9

Go to Step 13

9

1. Measure the voltage between the vacuum control assembly supply voltage circuit of the vacuum control assembly and the appropriate control circuit(s) of the vacuum control assembly.
2. With a scan tool, command the appropriate solenoid ON and OFF .

Does the voltage measure near the specified values for each commanded state?

B+ (ON)

0 volts (OFF)

Go to Step 14

Go to Step 10

10

Does the voltage remain near the specified value with each command?

B+

Go to Step 12

Go to Step 11

Test the appropriate control circuit of the vacuum control assembly for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 18

Go to Step 15

Test the appropriate control circuit of the vacuum control assembly for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 18

Go to Step 15

Test the vacuum control assembly supply voltage circuit of the vacuum control assembly for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 18

Go to Step 15

Inspect for poor connections at the vacuum control assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 18

Go to Step 16

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

Did you find and correct the condition?

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Go to Step 18

Go to Step 17

Replace the vacuum control assembly. Refer to Vacuum Control Assembly Replacement .

Did you complete the replacement?

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Go to Step 18

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Replace the HVAC control processor. Refer to HVAC Control Processor Replacement .

Did you complete the replacement?

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Go to Step 18

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Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2