cannot get new 250-1223 rostra cruise to set even though all self diagnostic tests pass. final test is road test and will not engage. This is on a 1993 diesel pusher with allison md3060 tranny.All switches seem to be set okay or why would self test pass. old rostra vacuum cruise worked but leaked down air pressure and no more parts. All wires where existing as to the switch. VSS wire has not been changed which also powers the speedo and works. The brake relay is clicking and working. Ground seems to be good. Cruise cable is adjusted with 1/8th inch play. Rostra teck is trying to help ,but i think he is starting to hide.????