What does the blue air line do on a tractor trailer?
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. We recommend starting with the blue line since it is the farthest away.
What is the blue air brake button for?
The yellow one controls brakes on all axles, the red is only for trailer, and the blue is only for the truck unit.
When Should air be supplied to the trailer brakes?
The warning system devices should come on before the air pressure drops below 60 psi in either system. If one air system is very low on pressure, either the front or the rear brakes will not be operating fully. This means it will take you longer to stop.
What Colour line shouldn’t you connect to the trailer?
Explanation: When connecting a three-line tractor unit to a two-line trailer, the blue line is the one that shouldn’t be connected to the trailer.
What is the emergency air line for?
Emergency air line: The emergency line (also called the supply line) has two purposes: (1) To supply air to the trailer air tanks, and (2) to control the emergency brakes on combination vehicles. Loss of air pressure in the emergency line causes the trailer emergency brakes to come on.
What is the red button in a semi truck?
trailer supply valve
When it comes to the red button — the trailer supply valve that controls the tractor protection control valve — there is an FMCSA regulation covering trip pressure.
What is the red knob in a semi?
Pressing the red knob supplies air through the red line to fill the reserve tank on the trailer, inflate the air suspension, and release the brakes. Pressing that knob also opens the valve for the blue line, which supplies air to the service side of the brake chambers when the brake pedal is pressed.
How can you test the airflow to all trailers?
Check that air flows to all trailers: Use the trailer hand brake to provide air to the service line. Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged.
Why is the air coming out of my trailer brakes?
If its blowing back though the service on the trailer as the video shows it is likely either the service brake relay valve on the trailer or the spring brake valve on the trailer. It’s blowing back thru the blue service port with line disconnected from trailer.
Why is air leaking from the Blue Line?
Red dash valve is IN (NO BRAKE APPLICATION), air is coming forcefully out the red dash valve, and there is air coming out of the blue glad hand, then the leak is internally in the TPV, between the Supply and the Service side. When you teach air brakes, the TPV and the Spring Brake Modulator are the most fun to teach.
When do trailer brakes need to be applied?
The tractor has park brake applied when it happens also when released. Every month 400 people find a job with the help of TruckersReport. Please Select… I Need CDL Training In CDL School Now CDL Grad, No Experience 1-5 Months 6-11 Months 1 Year 2 Years 3 Years 4 Years 5+ Years
How are trailer brakes compounded by a tractor?
24. Trailer brakes which have a spring brake control valve can be compounded by the tractor air brake system. The compounding occurs when service air pressure is trapped in the trailer service line by the tractor protection valve when the supply line is released to atmosphere.