H Miller, welcome to iRV2.com. We are glad to have you join us here and we look forward to reading of your adventures and experiences. Does the vacuum pump cycle off? If not you do have a leak as Dick has stated. If it does cycle on and off when you pull a hose off then you may have a solenoid valve not getting voltage or is bad. You can run a hose straight from the pump to the damper control for the dash/defrost damper control to get you by if you need to get to where you are going. You would want to block of the fresh air intake or tee in a line and feed that damper as well to keep outside air from mixing in.
Good luck and keep us posted. Enjoy the website.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7