20 - 45 psi. The trailer protection valve is designed to close automatically if the air pressures becomes too low (i.e., drops to a range of 20-5 psi)
You should always test the trailer brakes before driving with the hand valve or by pulling the air supply control.
Wheel chocks. In trailers without spring brakes, the brakes will hold only as long as there is air pressure in the trailer air tank. If the air leaks away, there will be no brakes. Therefore, wheel chocks should be used to secur
Glad hands is used to connect the service and emergency air lines from the truck to the trailer.
Fifth wheel plate. When coupling tractor-semitrailers you need to insure that the fifth wheel plate is greased as required so that friction between the tractor and trailer does not cause steering problems. Relay valves (which conn
Turn the crank in low gear a few extra turns after firm contact with the ground. If you turn the crank in low gear a few extra turns, it will lift some weight off of the tractor which will make it easier for you to unlatch the fift
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