What position should the tractor protection valve be in?
A tractor protection valve (Fig. 38) is usually mounted on the cab or chassis of the tractor. When the trailer-supply valve is open, air passes through the bottom of the tractor protection valve and charges the trailer through the supply line (also called the emergency line).
What is the tractor protection control valve?
The TSV is sometimes also referred to as the “tractor protection control valve”. The TPV serves as the on/off port for signaling service brake air going to the trailer. It is the connection point for both the trailer supply/emergency line and the trailer service line.
What is crack pressure on a relay valve?
Crack pressure is the air pressure value required at the input from the foot valve before the relay valve will send air pressure to the brakes controlled by that valve. Too high a crack pressure can cause delayed application, insufficient braking and trailer pushing, if the affected axle is on the trailer.
At what pressure will the protection valve for your trailer pop out?
20 to 45 psi
Trailer air supply control: Pushing it in supplies the trailer with air, and pulling it out shuts the air off and puts on the trailer emergency brakes. The valve will pop out and close the tractor protection valve when the air pressure drops into the range 20 to 45 psi.
What happens to the trailer emergency brakes if there is a loss of pressure in the emergency line?
The emergency brakes to activate. The emergency air line controls the emergency brakes on a combination vehicle. A loss of air pressure in the emergency line will cause the emergency trailer brakes to activate.
Where are the shut off valves located on a tractor trailer?
The tractor protection valve itself is located at the point under the tractor’s frame where the flexible airlines that go to the trailer are connected by the coupling devices called glad hands.
What is the emergency relay valve?
The relay emergency valve has a one-way check valve that stops air in the reservoir from going back to the source of the supply. The driver has opened the trailer-supply valve to allow main-reservoir air pressure to be directed through the tractor protection valve to the trailer.
What does a brake pressure relay do?
A brake light switch is sometimes called a brake relay. This is the switch that tells your car’s computer and lights that you’ve pressed the brakes. This sends a signal to turn the lights on and also allows you to shift out of park, or in some cases, turn your car on.
What would happen if the emergency red air line between the tractor and trailer came apart?
Your emergency air line breaks or gets pulled apart while you are driving. The loss of pressure will cause the: a. Emergency trailer brakes to come on.