Schematic Reference: HVAC Schematics .

DEFINITION: The temperature cannot be adjusted or the heating is insufficient.

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 operate in any of the speed positions?

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Go to Step 3

Go to Blower Motor Inoperative

Does the blower actuator operate correctly for each speed position?

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Go to Step 4

Go to Blower Motor Malfunction

Is the HVAC control module inoperative?

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Go to Step 17

Go to Step 5

Inspect the cooling system for the following:

Did you find and correct the condition?

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Go to Step 24

Go to Step 6

1. Start the engine.
2. Place the blower motor switch in the OFF position.
3. Place the A/C request 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. Turn ON the ignition, with the engine OFF.
2. Observe the drive shaft of the air temperature door actuator.
3. Adjust the air temperature switch.

Does the air temperature door 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 door actuator for the following conditions:

Did you find and correct the condition?

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Go to Step 24

Go to Heating Performance Diagnostic

Test the ignition 3 voltage circuit of the air temperature door 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?

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Go to Step 24

Go to Step 10

Test the ground circuit of the air temperature door 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 24

Go to Step 11

Test the 5 volt reference circuit of the air temperature door actuator for an open, a high resistance, short to ground, or a 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 24

Go to Step 12

Test the air temperature door position signal circuit of the air temperature door 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 24

Go to Step 13

Test the air temperature door control circuit of the air temperature door 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 24

Go to Step 14

14

Important:: The air temperature door actuator connector and the HVAC controller connector must be connected to correctly perform tests.

1. Turn ON the ignition, with the engine OFF.
2. Backprobe and monitor the voltage from the air temperature door position signal circuit of the air temperature door actuator to a good ground.
3. Connect a 3 amp fused jumper wire between the air temperature door control circuit and the 5 volt reference circuit of the air temperature door actuator (drives the actuator full COOL).
4. Remove and reconnect the jumper wire between the air temperature door control circuit and the ground circuit of the air temperature door actuator (drives the actuator full HOT).

Does the air temperature door actuator drive shaft rotate and does the voltage change?

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Go to Step 15

Go to Step 19

1. Backprobe the air temperature door actuator connector terminal in order to measure the voltage from the air temperature door control circuit to a good ground.
2. Adjust the air temperature switch.

Does the voltage measure near the specified value when increasing air temperature, near the specified value when decreasing air temperature and near the specified value when stationary?

0 V increasing

5 V decreasing

2.5 V stationary

Go to Step 16

Go to Step 21

Inspect the air temperature door for a mechanical failure or a condition that allows excessive travel of the door.

Did you complete the repair?

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Go to Step 24

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Test the ignition 3 voltage circuit of the HVAC controller 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?

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Go to Step 24

Go to Step 18

Test the ground circuit of the HVAC controller 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 24

Go to Step 21

Inspect for poor connections at the harness connector of the air temperature door 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 24

Go to Step 20

Inspect the air temperature door 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 24

Go to Step 22

Inspect for poor connections at the harness connector of the HVAC controller. 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 24

Go to Step 23

Important:: Perform the recalibration procedure for the air temperature door actuator.

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

Did you complete the replacement?

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Go to Step 24

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Replace the HVAC controller. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

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Go to Step 24

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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