How to diagnose refrigerant flow:
with the unit running when it's working: stick you head
inside the fridge near the evaporator plate and listen. You should hear a gurgling sound which is the refrigerant evaporating. Check the lines on the plate and the spots where the refrigerant line is soldered on. Is there ice forming on the plate in that spot or over a larger area?
Now when the unit does not work
: stick your head
in again and listen. When the gurgling sound is gone, take a hair dryer or heat gun and heat that area where the line is soldered to the plate. If this makes the unit kick back in to gurgling and cooling
then you have moisture in the system, caused by a leak (often the O-rings when you have quick connect fittings and it's a couple of years old).
If this is the problem then the system needs to be checked for the leak location (replace O-rings, comes with spares), evacuated with a vacuum pump
and refilled. During evacuating, use the heat gun to heat all over the evaporator plate, the lines and the compressor incl. the brass "bulb" dryer. This promotes moisture boiling out of the oil
. You can hear the effect at the vacuum pump
immediately as it begins to sputter as soon as you hit parts
with moisture inside with the heat gun.
For filling: these systems should be filled by observation of the return line from the evaporator to compressor. Don't forget to bleed the hoses, then fill with system turned off to bottle pressure. Then close all valves and start system. Only add refrigerant on the low side (the cold return line) and fill so that this return line starts sweating. If it starts freezing, there is too much refrigerant in the system. This is fool proof and optimal fill level