Freezer Room

not enough info...as usual. you're really making me wonder why you took the txv apart to get to the orifice??? did you find it obstructed when you got to it
/ I bet it was perfectly normal

Every time you open the door to check the temperature you introduce the room air.

Maybe this is why you dont get to a lower temperature with your measurement.

Just a guess!

Why did you do what you did?

Any technical reason for those changes?

Do you have any training that qualifies you for refrigeration troubleshooting and repair?

My advice: Call a qualified repairperson.

Because of the repeated low pressure cutoff, I suspect loss of refrigerant charge. Please check for leaks, repair any that are found, and replenish any lost refrigerant.

Possibly low on refrigerant, possibly valves worn in compressor, possibly bad tx valve....Possible air in system......What is the drop across the coil at temp ? Is the defrost cycle completely removing ice ? What is the temp rise across condenser coil ? How many defrost cycles per 24 hrs ?

I wish you gave more quality info. I'll try again. since this 10 degree number seems important to you lets start there. first off you want to verify the thermocouple, thermistor or thermometer is giving you an accurate reading, not fooling you. so take another reading with a trusted instrument and calibrate to eliminate this factor. assuming thats all good lets move to evaporator air flow. you didn't supply a picture (wow I'm shocked) so I'll take a wild guess it has 2 fans ( could be a very different number. lets make sure these are unobstructed, spinning in the right direction, fan blades aren't upside-down etc. and of course your coil is NOT frozen when you're testing airflow.

referring back to the high pixel picture you provided of the liquid line..opps!, thats right, no pic. if the coil is ice free does it have a sight glass? under full load is the glass running clear? a tiny stream of bubbles, huge stream of bubbles? when you opened the txv did you blow thecharge, pump the system down, use a receiver..weight in a complete new charge??? is this a 404 system? are you confident you have the right refrigerent in the right amount in the system to perform your tests, are you using a decent set of dedicated gauges or are you mixing CFC and HFCs?

so many questions, so little info, no pics you verified the cut off switch is engaging at the right set point as shown on your gauges, right?

Sharing the maintenance records on this equipment would be valuable.