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Air Delivery Improper



Air Delivery Improper

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information






Circuit/System Description

The mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 7.5-11 volts. When the module sets a commanded, or targeted, value, the control signal is changed to either 7.5 or 11 volts depending upon the direction that the actuator needs to rotate to reach the commanded value.

Diagnostic Aids

Inspect the mode door and the mode actuator for the following conditions:

* A misaligned mode actuator.
* Broken or binding linkages or mode door.
* An obstruction that prevents the mode door from operating within its full range of motion.
* Missing seals to the mode door.
* Misaligned seals to the mode door.

Circuit/System Verification

1. Ignition ON, command the blower motor from Off to Low through High by changing the blower motor switch from Off through to the High speed positions, the blower motor should turn ON and operate from Low to High when changing between the commanded states.

^ If the blower motor speed does not change or fails to operate at a selected speed, refer to Blower Motor Malfunction. Blower Motor Malfunction

2. Rotate the mode control switch to the VENT, BI-LEVEL, FLOOR, FLOOR/DEFROST and DEFROST positions. The air flow should follow the commanded states and blow through the vent, floor and defrost outlets.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the mode actuator.
2. Test for less than 1.0 ohm between the low reference circuit terminal 1 and ground.

^ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.

^ If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
^ If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

4. Verify the scan tool Mode Dr Actual parameter is less than 3 counts.

^ If greater than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the HVAC control module.

5. Install a 3A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool Mode Dr Actual parameter is greater than 250 counts.

^ If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

6. Connect a test lamp between control circuit A terminal 4 and control circuit B terminal 5.
7. Command the mode door in both directions with a scan tool. The test lamp should turn ON and OFF with each command.

^ If the test lamp remains always ON or always OFF during either commands, test for an open, short to ground, or short to voltage on either control circuit. If the circuit tests normal, replace the HVAC control module.

8. If all circuits test normal, replace the mode actuator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Mode Actuator Replacement.
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