Final answer:
To check a slack adjuster, park on level ground, turn off the parking brakes, and pull on each slack adjuster which should not move more than one inch, indicating proper adjustment.
Step-by-step explanation:
To check the slack adjuster on a vehicle, primarily in a commercial truck or bus that has air brakes, you should follow a standard procedure. The most commonly recommended method is the first option:
- Park the vehicle on level ground to ensure safety and the accuracy of the check.
- Ensure the parking brakes are turned off. This is because the slack adjusters can only be accurately checked when they are under tension, which isn't the case when the parking brakes are applied.
- Pull hard on each slack adjuster. It should not move more than one inch, which indicates that it is within proper adjustment limits. If it moves more than this, it may require adjustment or further maintenance.
The other methods listed, such as pressing the brake pedal or parking on an incline, are not standard methods for checking slack adjusters and might not provide accurate information about their condition.