I am new to this site as well as fairly new to the refrigeration repair end of the business. have done HVAC for a number of years as well as some refrigeration work. Took a new job with a local school district and have been thrust into the refrigeration world.

We have a walk-in freezer (404A) small unit box is 6'x6' that recently had the TXV changed by the former tech. Only about 8' of piping between cond and evap. Unit came down to temp initially but then lost some refrigerant and quit working. Enter Tom in the picture.I did some intial testing and found a leak on a service valve as well as a leak in the piping. pressure tested and evacuated the system down to 500 microns. System appeared to 1st hold pressure for 2 hours as well as the vacuum for a couple of hours. Charged the system yesterday with aprox. 6# 404A as well as about 1 oz. flourescent dye. Site glass was fulland clear
Box came down to temp overnite and when I checked this morning box was at about +9 and operating just fine. Checked for any sign of leaks and saw none with the UV lite. Had a compressor to put in and did not get back today but my boss was by and said there were bubbles (flashing?) in the site glass.

We are in 100 degree temps in MO and the box was well over 90 inside when I initially charged it yesterday. There may be a leak I have not found but I did a pretty thorough check at at this point if it is aleak it must be in one of the coils where I have yet to see it. After all this the question I want to ask at this point is: Is it possible that the system may need additional refrigerant after it reached operating temp. Could the site glass give a "false" reading due to the high temps in the box? TXV seems to be working OK and I was waiting to tweak the superheat when it was down to operating temps.

Thanks in advance for your input. I am enjoying the challenge but this one has me somewhat stumped.