Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The HVAC control assembly is inoperative when the assembly does not respond to an operator control request.
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If no condition found with all conditions listed then compare door travel to known good vehicle.
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The voltage will vary between 0-5 volts during normal operation. Ensure to observe the air temperature actuator driveshaft and the volt meter when jumping the control circuit with 5-volt reference and the ground circuits. The air temperature actuator and the HVAC control assembly connectors must be connected during this step.
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics DEFINITION: The temperature cannot be adjusted or the heating is insufficient. | ||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||||
2 |
Does the blower operate in any of the speed positions? | -- | Go to Step 3 | Go to Blower Motor Inoperative | ||||||||||||
3 | Does the blower motor operate correctly for each speed position? | -- | Go to Step 4 | Go to Blower Motor Malfunction | ||||||||||||
Is the HVAC control assembly inoperative? | -- | Go to Step 17 | Go to Step 5 | |||||||||||||
5 | Inspect the cooling system for the following:
Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 6 | ||||||||||||
6 |
Does the A/C compressor operate? | -- | Go to Step 7 | |||||||||||||
7 |
Does the drive shaft of the air temperature door actuator ever rotate? | -- | 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? | -- | Go to Step 24 | ||||||||||||||
9 | Test the ignition 1 voltage circuit of the air temperature actuator for an open or for a high resistance. Refer to Circuit Testing and to Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 10 | ||||||||||||
10 | Test the ground circuit of the air temperature actuator for an open. Refer to Circuit Testing and to Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 11 | ||||||||||||
11 | Test the 5-volt reference circuit of the air temperature actuator for a high resistance. Refer to Circuit Testing and to Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 12 | ||||||||||||
12 | Test the signal circuit of the air temperature actuator for a high resistance. Refer to Circuit Testing and to Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 13 | ||||||||||||
13 | Test the control circuit of the air temperature actuator for a high resistance. Refer to Circuit Testing and to Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 14 | ||||||||||||
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Important: Ensure the air temperature actuator connector and the HVAC control module connector are connected during this step in order to avoid misdiagnosis.
Does the drive shaft of the air temperature door actuator rotate and does the voltage change? | -- | Go to Step 15 | Go to Step 19 | |||||||||||||
15 |
Important: Ensure the air temperature actuator connector is connected during this step in order to avoid misdiagnosis.
Is the voltage measurement near the specified value for each condition? | 0 V increasing 5 V decreasing 2.5 V stationary | Go to Step 16 | Go to Step 21 | ||||||||||||
16 | Inspect the air temperature door for a mechanical condition or for a condition that allows excessive travel of the door. Did you complete the repair? | -- | Go to Step 24 | -- | ||||||||||||
17 | Test the ignition 1 voltage circuit of the HVAC controller for the following:
Refer to Circuit Testing and to Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 18 | ||||||||||||
18 | Test the ground circuit of the HVAC controller for an open. Refer to Circuit Testing and to Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 21 | ||||||||||||
19 | 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. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 20 | ||||||||||||
20 | Inspect the air temperature actuator, the door, and any attaching linkage, for binding or for a condition that prevents drive shaft rotation. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 22 | ||||||||||||
21 | 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. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 23 | ||||||||||||
22 |
Important: Perform the calibration procedure for the air temperature actuator. Replace the air temperature door actuator. Refer to Temperature Valve Actuator Replacement . Did you complete the replacement? | -- | Go to Step 24 | -- | ||||||||||||
23 | Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement . Did you complete the replacement? | -- | Go to Step 24 | -- | ||||||||||||
24 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 | ||||||||||||
