CDL Question of the Day: When testing air flows to all trailers, what is the first step?
- Wait for the air pressure to reach normal, then push in the red ”Trailer air supply” knob.
- Chock the wheels or use the tractor parking brake.
- Open the service line valve to check that serve pressure goes through all the trailers.
- Use the trailer handbrake to provide air to the service line.
Answer: B. Use the tractor parking brake and/or chock the wheels to hold the vehicle. Safety is always first.
Here are the steps to testing air flows to all trailers:
“ Use the tractor parking brake and/or chock the wheels to hold the vehicle. Wait for air pressure to reach normal, then push in the red “Trailer air supply” knob. This will supply air to the emergency (supply) lines. Use the trailer handbrake 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. Close the emergency line valve. Open the service line valve to check that service pressure goes through all the trailers (this test assumes that the trailer handbrake or the service brake pedal is on), and then close the valve. If you do NOT hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly(ies) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.”
STATE OF UTAH, Department of Public Safety Driver License Division. March 2009. Section 6, Combination Vehicles, Pages 6-11