Tractor Protection Valve

[leversole]

Looking at the air piping digram in the service manual and wanted some clarification. It looks like the trailer protection control valve gets its supply from the spring brake valve, so, when you park, do you just pull the spring brake valve to set the truck brakes,and the trailers brakes are set automatically (does the trailers supply "pop" out?)? Or do you pull both valves to individually set the truck and trailer brakes?

Thanks

[towboy999]

When you pull out on the yellow supply button the trailer brake button (red) should pop out automatically. With a little pressure on the red button while pulling out on the yellow will prevent the trailer brakes from being set.

[Rob]

When you pull out on the yellow supply button the trailer brake button (red) should pop out automatically. With a little pressure on the red button while pulling out on the yellow will prevent the trailer brakes from being set.

On my trucks I can release the trailer brakes independently of the tractor. I can also set the trailer brakes while releasing only the tractor brakes. With the tractor and trailer brakes set, I can mash the red button independent of the yellow button and it will release the trailer brakes but leave the tractor brakes set. With both tractor and trailer brakes released, pulling on the yellow botton will set both tractor and trailer brakes at the same time. With all brakes released, pulling on the blue know sets only the tractor brakes.

Rob