Hello! Need help please. The yellow knob is not popping out.

I just don’t understand how a loss of air on the trailer supply and the yellow knob not popping out would make an unsafe condition.
If you have a loss of air on the trailer supply, the red button should pop out to stop the leak and prevent a total system loss. After that, I think it would be advantageous for the yellow button to remain in where you still had truck service brakes to get stopped in a safe fashion. I just don’t seen how locking the truck brakes when the leak is contained to the trailer can help you make a safe stop.

 

If pressure drops.

Both are supposed to pop.

Doesn't matter how it's done.

But who disconnects the trailer without parking the truck?

 

The knobs pop at 40 or less.
The alarm sounds at 60-70.

The alarm makes you stop before the knobs pop.

I seem to recall something about the knobs being a safety device to stop. If pressure drops to that point.

Have you ever paid attention to what the pedal feels like as air gets lower?

And here's another thing..some of you comment as if the trailer and truck are 2 separate devices on the air pressure.

It don't matter if you have a leak in trailer or truck. The entire system loses pressure. There's no separation between the 2.

Air leaks usually happen when the brakes are applied. Most times it's the brake can. Sometimes I've had the brake line go. A few times I've had the air bag go.

I've had other leaks but cans and pressure hoses and bags have been my experience anyways.

Vice grips should be #1 truckers friend. You can always pinch off the air line to get you somewhere.

 

No it is not bad.

 

My air dryer has a changeable filter, and I change it once a year.