is it ebpv problems

[rick miller]

i have a exaust brake that works througe the ebpv.problem is when the engine is cold i can flip the switch and it works wellbut when reaches not it does nothing to hold back truck.i can raise the hood and have someone flip the swithh and i can see the actuator arm go its distance but there is no change in engine or exaust sound.but it works fine before engine gets hot.i would appreceate any help that anyone has to offer we have tried to fix this problem for two years.