Arizona Air Brakes CDL Practice Test

If your air compressor stops working, what happens to the air pressure?

1. You'll lose your brakes immediately

2. The brakes will immediately lock up

3. You'll still have air pressure left in the air tanks

4. Your brakes won't be affected

The correct answer is: You'll still have air pressure left in the air tanks

When the air compressor stops functioning, it does not lead to an immediate loss of air pressure in the brake system because the air tanks still contain a reserve of compressed air. These tanks act as a storage system for air that has been pressurized by the air compressor when it was operational. This remaining air pressure allows the brake system to continue functioning for a while, giving you a window of opportunity to react, such as finding a safe place to stop the vehicle. It is important to monitor the air pressure gauge during operation; if the compressor fails, over time the stored air will deplete as the brakes are used. In contrast to this understanding, the other options imply immediate and negative consequences that do not accurately reflect the function of the air brake system. The brakes will not lock up suddenly or be instantly affected since they rely on the reserve air pressure present in the tanks at the moment the compressor stops working.