[Richard]

It is important to flood the internals with Nitrogen before soldering. If you don’t oxides form on the interior of the copper pipes, and then they can contaminate the refrigerant with flakes of the oxides. No matter if the system is capillary tube like the dometics or thermal expansion valve like the SCS units, the oxides stop up the expansion orifice. Tell tell signs of stopped up or non functioning expansion device are low LOW side and high HIGH side.

Did the radiator shop use SilFos (silver solder) or their normal 50/50 lead tin solder?

Post the dimensions of the coil, and how many rows of tubing it has. Maybe we can find you a new one.