Review Questions - Click On The Picture To Begin...
- On double and triple trailers, the tractor protection valve will not work
- Step on and off the brake pedal several times to reduce the air pressure in the tanks until the trailer air supply control pops out
- Engage and disengage the parking brake repeatedly until the trailer air supply control pops out
- Chock the wheels, release all brakes, then go to the last trailer and open the shut off valve to release as much air from the system as possible to see if the trailer air supply control pops out
Quote From The CDL Manual:
Test tractor protection valve: Charge the trailer air brake system, (i.e., build up normal air pressure and push the "air supply" knob in). Shut the engine off. Step on and off the brake pedal several times to reduce the air pressure in the tanks. The trailer air supply control (also called the tractor protection valve control) should pop out (or go from "normal" to "emergency" position) when the air pressure falls into the pressure range specified by the manufacturer (usually within the range of 20 to 45 psi).
- Both the service line and emergency line should be in the closed position
- The service line should be closed and the emergency line should be open
- The service line should be open and the emergency line should be closed
- Both the service line and emergency line should be in the open position
Quote From The CDL Manual:
Check air flow 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), 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 (5) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.
TruckingTruth's Advice:
All shut-off valves on the rear most trailer should always be in the closed position.
- The service line should be open and the emergency line should be closed
- Both the service line and the emergency line should be closed
- Both the service line and the emergency line should be open
- The service line should be closed and the emergency line should be open
Quote From The CDL Manual:
Check air flow 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), 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 (5) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.
TruckingTruth's Advice:
Unless it is the very last trailer, all shut-off valves should remain in the open position so that all trailers have proper airflow in the air brake system.
- 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 yellow "tractor air supply" knob
- 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
- If you do NOT hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly are in the OPEN position
Quote From The CDL Manual:
Check air flow 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), 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 (5) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.
- The service line should be open but the emergency line should be closed
- Both the service line and emergency line should be in the closed position
- Both the service line and emergency line should be in the open position
- The service line should be closed but the emergency line should be open
Quote From The CDL Manual:
Check air flow 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), 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 (5) are in the OPEN position. You MUST have air all the way to the back for all the brakes to work.
TruckingTruth's Advice:
Unless it is the very last trailer, all shut-off valves should remain in the open position so that all trailers have proper airflow in the air brake system.