Cooler not cool enough!!!

[l3astardd]

Hello everyone, I have a SC-48-BM Cooler http://www.universalcoolers.com/products/sc_48_bm.html. The initial problem was that it wasn't cool enough (coldest temperature only reaches around 50 degrees F). I have replaced the expansion valve, compressor, filter, tubings/pipes, and it's still not hitting the 30 degrees F (although it reach the 30s when I replaced the compressor but malfunctioned again after 2 weeks). Some experts are telling me I should replace the expansion valve with Capillary tubing. Anyone have any ideas? any kind of input is very much appreciated. thank you!

[passandscore]

What type of refrigerant are you using? What are your operating pressures when it is running? What's your superheat set at? Start with the basics! Why would you replace the piping? Which piping? All of it? You have done a lot of work and that is unfortunate seeing as a replacement cooler costs $1300.00

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[monkey spanners]

Evaporator and condenser coils clean?
All fans working, blades on right way round and spinning correct direction?
Door seals good?
Defrost system working ok?
Correct refrigerant charge?
Drain clear?
User error?
Air on and air off temps will help point you in the correct direction as would superheats and subcooling measurements.