tcmwhite

I have a 2009 Winnebago. My air dryer keeps blowing off air only while I am driving. It blows off for a few seconds and then stops and starts again in another few seconds. I replaced the purge valve, air dryer filter, governor and supply line from the governor to the air dryer. I know my unloader valve in the compressor works cause I can hear it cycling and notice the air changes. Is there something I am missing? Thoughts????