Trailer brakes not working

.... and I’ve chaged the pop out valves

 

Hello GrapeApe,
I'm facing the similar problem. however I would number my situation and we go from there.
1. Hook up trailer lines, Push Red Knob in Supply air to trailer and Spring brakes released.
2. Spike Brakes/Manual Brakes work fine but no air exhaust noise coming in.
3. Apply Foot brakes but trailer brakes not applying.
4. Pull Red knob out but trailer spring brakes not applying and trailer is still rolling until red supply line is removed air backfields from red glad hand then only
brakes apply.
5. Changed Tractor Protection Valve but no good.
What else could go wrong. Please advice. Thanks

 

I have run into this several times where the plastic air line gets kinked on the
inside of where it attaches to the bulkhead connector at the glad hand. Can
you pull the panel with the glad hands on it out and have a look?

 

I am having the same issue. What was the solution to your problem?

 

I too am having this issue with my flatbed. Ever since I bought the trailer it would dump all the air out of the bags when I set the brakes. I figured this was just a trailer feature. As of recently that trailer has no brakes just like this guys.they don’t work at all. They release, and the air bags will inflate but no service brakes. All brakes are in adjustment. My van trailer works normally and the tractor is putting pressure through the blue line so it’s the flatbed with the problem for me. But you guys are mentioning a handful of different valves so I’m trying to understand the flow of the air here in kind of a linear form so I understand the air system on my trailers. I can release my brakes and I have air in the bags but no service brakes.