1. Remove the VAD check valve (one-way). (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION)
2. Blow through A and verify that air flows from B.
3. Blow through B and verify that air does not flow from A.

Variable air duct (vad) control solenoid valve inspection (l3)
Idle air control (iac) valve inspectionMazda 6 Service Manual: Fuel tank inspection
Caution
Disconnecting/connecting the quick release connector without
cleaning it may possibly cause damage to the fuel pipe and quick release
connector. Always clean the quick release connector joint area before
disconnecting/connecting using a cloth or soft brush, and make sure that it ...
Mazda 6 Service Manual: Generator removal/installation
Warning
When the battery cables are connected, touching the vehicle body with
generator terminal B will generate sparks. This can cause personal injury, fire,
and damage to the electrical components. Always disconnect the battery negative
cables before performing the following operation.
...