Every combination vehicle has two air lines—the service line and the emergency line. They run between each vehicle (tractor to trailer, trailer to dolly, dolly to second trailer, etc.).
What is the blue airline on a semi?
The blue line is the service brake air line. when the foot valve is applied to apply the tractor brakes, this applies the trailer brakes.
What are the blue and red glad hands?
Gladhands are designed to allow the driver to disconnect without a mechanic or tools. Gladhands are color coded. In North America, service lines are blue and emergency brake lines are red and are standardized by SAE International's standard SAE J318.
What is the red air line on a truck?
The red line is the air line for the trailer's emergency brake. The green line is the electrical line. The blue line is the air line for the trailer's service brake. Connect these lines to the corresponding couplers and socket on the trailer before moving the trailer.
What does the red air line do?
Emergency air line (normally red): The emergency line has two purposes. First, it supplies air to the trailer air tanks and secondly, the emergency line controls the emergency brakes on combination vehicles. Loss of air pressure in the emergency line causes the trailer emergency brakes to come on.
What color is the supply line on a tractor trailer?
red
What are the red and blue air lines for trucks?
Air and Electrical Lines The red line is the air line for the trailer's emergency brake. The green line is the electrical line. The blue line is the air line for the trailer's service brake. Connect these lines to the corresponding couplers and socket on the trailer before moving the trailer.