Combination Vehicles 1

You can confirm that air is going to all brakes in your trailers by

• Opening the emergency line shut off valve and then the service line valve at the rear of the last trailer and listening for air escaping each time.

• Opening the emergency line shut off valve at the rear of the last trailer and listening for air escaping.

• Confirming that the air pressure is at normal levels.

If the trailer has anti-lock brakes ( ABS) but the tractor doesn’t,

• The trailer is more likely to swing out.

• The trailer is still less likely to swing out.

• It doesn’t make it more or less likely that the trailer will swing out.

If your test of the tractor protection valve is successful,

• The low air pressure warning signal will come on.

• The parking valve will pop out.

• The tractor protection valve control (trailer air supply control) will pop out or go from “normal” to “emergency”.

As part of your vehicle inspection test, if your vehicle is equipped with air brakes and has a trailer, you will inspect the air connections between the truck or tractor and the trailer. Make sure that the ______ are locked in place and free of damage or air leaks.

• Pins

• Lugnuts

• Glad hands

To test the tractor protection valve, charge the trailer air brake system, turn off the engine, and

• Stepped on and off the brake pedal several times.

• Keep pressing the brake pedal firmly.

• Flash your highbeam headlights on and off several times.

After coupling, make sure that the airlines are not crossed. How should you do this?

• Turn off the engine and listen for the release of air as you apply the brakes.

• Adjust the air supply knob to send air to the trailer brakes. Turn off the engine once the air pressure normalizes. Then listen for the sound of escaping air as the brakes are released.

• Adjust the air supply knob to send air to the trailer brakes and check if the air pressure normalizes.

After you lock the kingpin into the fifth wheel, you should check the connection by pulling

• Forward 50 feet, then turning right, and then left.

• The tractor ahead sharply to release the trailer brakes.

• The tractor ahead gently with the trailer brakes locked.

Even before antilock braking systems (ABS) were required, some vehicles already had them. How can you check if your vehicle has ABS?

• Look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes.

• Brake the vehicle on a slippery road and see if the wheels lock.

• Look under the vehicle for the ABS test light.

When you’re pulling doubles or triples, the shut off valves should always be

• Open except for those on the last trailer.

• Open except for those on the first trailer.

• Open.

The tractor protection valve is designed to close automatically when the air pressure falls into the pressure range specified by the manufacturer, typically

• 20 to 45 psi

• 75 to 100 psi

• 50 to 75 psi