Schematic Reference : HVAC Schematics

DEFINITION: The temperature cannot be adjusted, or the heating is 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 blower motor switch 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 at the desired speeds?

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Go to Step 4

Go to Blower Motor Malfunction

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

Does air flow from the correct air outlets for each mode position?

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Go to Step 5

Go to Air Delivery Improper

5

Inspect the cooling system for the following conditions:

Refer to Heating Performance Diagnostic in Heating, Ventilation and Air Conditioning.

Did you find and correct the condition?

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Go to Step 17

Go to Step 6

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 drive shaft on the air temperature actuator ever rotate?

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Go to Step 7

Go to Step 8

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 17

Go to Step 8

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

Did you find and correct the condition?

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Go to Step 17

Go to Step 9

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

Did you find and correct the condition?

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Go to Step 17

Go to Step 10

Test the door control circuit of the air temperature actuator. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 17

Go to Step 11

11

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 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.

Is the voltage measurement within the specified values with a smooth transition between cold and hot?

0-12 V

Go to Step 14

Go to Step 12

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

Did you find and correct the condition?

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Go to Step 17

Go to Step 13

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

Did you find and correct the condition?

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Go to Step 17

Go to Step 15

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

Did you find and correct the condition?

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Go to Step 17

Go to Step 16

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

Did you complete the replacement?

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Go to Step 17

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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 17

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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