A040

Diagnostic Chart:

CIRCUIT DESCRIPTION
The ACP supplies voltage to an internal motor which drives the air mix door. The ACP monitors mix door position feedback from a sensor on the motor. If the mix door is requested to move but the feedback voltage does not change, the ACP stores Code A040. If the air mix door feedback indicates it is near the hot or cold extreme, the code will not set. Operation of the air mix door can be evaluated through self diagnostics as described in note 1 below.

TEST CONDITION(S)
1. Commanded Mix Door greater than 0%.
2. Commanded Mix Door less than 76%.

FAILURE CONDITION(S)
1. Actual Mix Door not within 3% of commanded Mix Door Position within approximately 60 seconds.

ACTION TAKEN
None.

NOTES ON FAULT TREE
1. ACP override AS12 allows for direct control of the HVAC mix door with the "WARM/COOL" buttons (the ECC will display the current commanded air mix door position as a value between 1 and 99). After selecting AS12, pressing "OFF" will allow for selection of a new test type. Selecting DATA, and then AD23, will enable the technician to command the air mix door to any position (via the "WARM/COOL" buttons) and observe the air mix door position sensor feedback (AD23) and its difference from the air mix door commanded position (AD22).
2. These readings indicate a fault, internal to the ACP, in the air mix door sensor feedback.
3. If the door is not stuck, ensure smooth operation before replacing ACP

NOTES ON INTERMITTENTS
If an intermittent code A040 is being set, select ACP Snapshot Data for Code A040 and note value of AD22 & AD23. Using override AS12 while monitoring AD23, command the door to these positions. Without keying off, physically inspect the mix door linkage for any obstruction at these positions.