• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Mode Door Control A | 1 | 1 | 1 | -- |
Mode Door Control B | 1 | 1 | 1 | -- |
5-Volt Reference | 1 | 1 | 1 | -- |
Mode Door Position Signal | -- | 1 | 1 | -- |
Mode Actuator Low Reference | -- | 1 | 1 | -- |
1. Mode Actuator Inoperative |
The actuators operate using 5 circuits. A 5-volt reference, low reference, signal circuit and two bi-directional 0 or 12 volt control circuits. The HVAC control module supplies a low reference and 5-volt reference to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. As the actuator door changes position the door position signal circuit voltage also changes. The two bi-directional control circuits enable the actuator to operate. Both circuits are set to 0 volts when the HVAC control module detects, from the feedback potentiometer, that the actuator is in the desired position. In order to move the actuator, the HVAC control module switches the appropriate control circuit to 12 volts.
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 |
Control Module References for scan tool information
⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. |
⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. |
⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. |
⇒ | If less than the specified range, test the signal circuit terminal 9 for a short to ground. |
⇒ | If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. |
⇒ | If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. |
⇒ | If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. |
⇒ | If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the HVAC control module. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for HVAC control module replacement, setup, and programming |