how to remove the trailer and parking air supply knobs

Might have to pull the knob out too.

 

Original truck I had the knobs kept vibrating loose,my daily pretrip came to include tightening the knobs. Discovered they were vibrating loose when the knob shot off when setting the brakes. I have video of what it looks like somewhere. Kind of funny, after the initial WTH response is done. I never glued them on, but thought about it a number of times. Dab of silicone caulk inside the threads took care of it finally.

 

Mind have a roll pin that hold the month of the shaft

 

Seen all three types. Roll pin, Set screw and the type that just screw on. The roll pin and set screw look about the same and are at base of the knob.

 

Look at the knob base nearest the dash spin/turn the knob if no hole screw on if one hole set screw (allen head) if two holes roll pin

 

Might sound silly. What brand of truck?The basic MV-2 valve look about the same if it's a fairly late model unit. Most do screw off, sometimes destroying the knob. Earlier valve were pinned/set screws. FWIW...never seen a MV-2,3,4 that didn't unscrew...but lots of things I haven't seen.

 

Don't forget the blue knob.