What is the primary function of a supply pressure gauge?

Answer: C — Tell you how much air is in the tank

The primary function of a supply pressure gauge is to tell you how much air is in the tank. This gauge provides crucial information regarding the air pressure within the air brake system of a commercial vehicle. Maintaining the correct air pressure is essential for proper brake operation, as it directly affects the performance and safety of the vehicle. Understanding the air pressure in the tanks helps drivers ensure that their braking system is functioning correctly and that there is enough air supply to operate the brakes effectively. In addition, it can alert the driver to any potential issues with the air compressor or leaks in the system that could compromise safety. This information is critical for a driver to make informed decisions and take necessary actions related to the vehicle's braking system.