Could be a blown out orifice tube. You really need a set of gauges to see what high side is reading. If orifice tube is blown out it will never get cold but you'll still have a system full gas. To verify hook up high and low side and the pressures will be nearly the same. The compressor will not kick on if the system is low as it has a pressure switch to prevent damage. Its not gonna be an interior blend door problem cause the lines would still be cold on low side and hot on high side and start forming ice on low side due to lack of airflow across evaporator coil. Could also be the valves in the compressor, but from my experience that don't just happen overnight its more if a wear out thing with the ones I've encountered. I think autozone may rent the gauges if you don't wanna spring for a set of your own.
