Quote:
Trailers will usually pop before the red knob does; that's the trailer's relay emergency valve response to the lowered supply pressure from the red gladhand.
there is no trailer valve that causes the red button to pop off. the valve pops off based on line pressure ; when pressure over the piston of the red pp valve is reduced to 20psi (20 to 45) the spring force under the piston pushes it out. that dumps emergency line pressure and then closes the tractor protection valve to isolate the trailer air system from the tractor
The trailer does this on it's own.
the tractor controls the air supply and service function to the trailer, the trailer only reacts to what it is told by the tractor
If you keep fanning off air, usually the trailer supply knob will pop next, and then the yellow one.[/quote
agreed
Read what I have written again- that's what I'm saying, bob. The trailer goes into emergency on it's own without any action from the tractor OTHER THAN low pressure in the supply line.Originally Posted by bob h
quote="JoeyB"]Quote:
Birken
Federal Motor Carrier Safety Regulations 393.43 (b) ..."One of these means shall operate automatically in the event of reduction of the towing vehicle air supply to a fixed pressure which shall not be lower than 20 pounds per square inch nor higher than 45 pounds per square inch"...Originally Posted by Birken Vogt
Quote:
State your sourceOriginally Posted by JoeyB
No, they must BOTH pop at 45-20, although not necessarily at the same time.
Birken
Trailers will usually pop before the red knob does; that's the trailer's relay emergency valve response to the lowered supply pressure from the red gladhand.
there is no trailer valve that causes the red button to pop off. the valve pops off based on line pressure ; when pressure over the piston of the red pp valve is reduced to 20psi (20 to 45) the spring force under the piston pushes it out. that dumps emergency line pressure and then closes the tractor protection valve to isolate the trailer air system from the tractor
The trailer does this on it's own.
the tractor controls the air supply and service function to the trailer, the trailer only reacts to what it is told by the tractor
If you keep fanning off air, usually the trailer supply knob will pop next, and then the yellow one.[/quote
agreed