ideally this expansion valve is wrapped in two wraps of cork tape - this isolates the valve itself from ambient air temperature. It provides a small increase in efficiency.
btw - if you visit HVAC market and ask for coil cleaner for supermarket display and meat chiller evaporators (food grade, self rinsing) - you can clean the coil very nicely with it. It literally pushes out each little piece of dirt from deep inside.
anyway, I hope you get the performance you require, if you used the PAG oil with R12, Then the whole system life is very short lived.
