Air comes out red line all time

Why does air come out red line when disconnected worse when applying brake

 

So nobody knows ?

 

This appears useless

 

Impatient much?

First why dont you start by telling us what your working on? Are you saying that air comes out the red trailer line all the time? Regardless of if the red knob is in?

 

Yes and it's a 91 fld

 

When applying the brake bobtailing all the air pressure comes out red line with very little stopping ability

 

It sounds like you have a valve stuck open on the trailer emergency air supply. If you are bobtail the red knob is pulled out and no air should be coming from the red emergency line.

 

So replace valve in dash?

 

Your post is a bit vague. Is your red trailer air supply knob pulled out?

This kind of feels like a troll post

 

Check your Tractor Protection Valve.