My 2013 Trail Runner, Airxcel 4800 13.5 series, air conditioner isn’t cooling. The unit is blowing cool air, not cold. I’ve messed with thermostat, cleaned filter, and cleaned the roof unit. Instead of spending money on things that, MIGHT, fix it, which I’ve tried. I’m looking into purchasing the upper roof unit. This isn’t as easy as I thought from google. Various units and sizes are brought up. Can I get any advice or tips from any of the members? Thanks