Heatcraft low temp unit w/high head lockout

[pyat]

Texas at 104 ambient, outside condenser, using 404a with a Copeland compressor and receiver tower. Box has a Bohn 5 fan evap and Sporlan expansion valve. We have very little gas going through the valve even when fully open. Changed the cap and bulb as it was not opening but did when placed in warm water. Still have only 20 psi at suction line and high pressure/temp protection on the compressor keeps kicking in. No blockage in line. Pumped down just fine. What would be the problem here? Compressor lost suction side? How do we ascertain? Expansion valve still bad? Compressor has bypass valve to put liquid in top of of compressor to cool and that valve has been constantly open. Any suggestions? Thanks

[mad fridgie]

What is your required box temp?
really do need a lot more data?
Have you cleaned the filter cage in the expansion valve?
What sound do you hear at the expansion valve?

[nike123]

Blockage before expansion valve.