I had the same issue with a Shasta. The vent pieces slide into each other and become corroded tightly together. I eventually pulled the vent apart but it took brute force. I agree with vikx, cap it. I might disconnect it under the camper and cap it there at (usually) a T fitting that branched off to the heater.
Have you considered replacing the unit with a Wave3?
Last Edit: Aug 18, 2020 4:14:43 GMT -8 by nccamper