Schematic Reference: HVAC Schematics

DEFINITION: Temperature can not be adjusted or heating insufficient.

1

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

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Go to Step 2

Go to Symptoms - HVAC Systems - Manual

1. Turn ON the ignition, with the engine OFF.
2. Place the mode switch in any position except OFF.
3. 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 3

Go to Blower Motor Inoperative

Does the blower motor operate correctly for each speed position?

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Go to Step 4

Go to Blower Motor Malfunction

Turn the blower motor fan ON and select an air outlet mode.

Does air flow out of the selected HVAC outlet ducts.

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Go to Step 5

Go to Air Delivery Improper

5

Inspect the cooling system for the following:

Did you find and correct the condition?

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Go to Step 18

Go to Step 6

1. Start the engine.
2. Place the mode switch in the OFF position.

Does the A/C compressor operate?

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Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 7

1. Observe the drive shaft of the air temperature actuator.
2. Place the air temperature switch from the coldest position to the warmest position.

Does the air temperature actuator drive shaft rotate at all?

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Go to Step 8

Go to Step 9

Inspect the air temperature door and the air temperature actuator for the following conditions:

Did you find and correct the condition?

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Go to Step 18

Go to Step 9

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

Did you find and correct the condition?

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Go to Step 18

Go to Step 10

Test the ground circuit of the air temperature actuator for 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 11

Test the air temperature control signal circuit of the air temperature 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?

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Go to Step 18

Go to Step 12

12

Important:: Ensure that the HVAC control assembly connector is connected during this step in order to avoid misdiagnosis.

1. Turn ON the ignition, with the engine OFF.
2. Measure the voltage from the air temperature door control circuit of the air temperature actuator to a good ground.
3. Place the air temperature switch from the coldest position to the warmest position.

Does the voltage measure within the specified values with a smooth transition between COLD and HOT?

0-12 V

Go to Step 15

Go to Step 13

Inspect for poor connections at the harness connector of the air temperature actuator. 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 14

Inspect the air temperature actuator, door and any attaching linkage for binding or a condition that prevents drive shaft rotation.

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 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 17

Replace the air temperature actuator. Refer to Temperature Valve Actuator Replacement .

Did you complete the replacement?

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Go to Step 18

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Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control 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