Need more details. What RV do you have? What part of HVAC is not working? HVAC is any equipment that keeps your RV at the desired temp, so it includes heater, a/c, heat pump, etc. Do you have one thermostat or zones?
Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder