How do you supply air to the trailer tanks?

Supplying air to the trailer tanks is achieved by pushing in the trailer's air supply valve. This action allows the air from the tractor's air system to flow into the trailer's air tanks, enabling the trailer's brakes to function properly. When the valve is pushed in, it creates a direct connection that pressurizes the trailer's air tanks with the compressed air produced by the tractor.

In contrast, pulling out the trailer air supply valve would prevent air from entering the trailer's tanks. Connecting the service line glad hand is important for establishing a connection between the tractor and the trailer, but it does not supply air by itself. Similarly, pushing in the tractor’s air supply valve is not the mechanism for directly supplying air to the trailer's tanks; it is the act of engaging the trailer's air supply valve that initiates the flow. Thus, pushing in the trailer's air supply valve is the correct method to ensure that the trailer has the necessary air pressure for its braking system.