The customer has side by side built-in refrigerator unit from Sub Zero brand. The initial problem was Sub Zero 642 refrigerator no cold. She explained to me that the refrigerator side was getting warmer and she had ice build up on the back wall.
Frost on the back wall is the first sign for me that the sealed system is low on the refrigerant. I removed the top grill part and hooked up my gauges to measure the pressure. My gauges showed me negative pressure below 0 psi. This is the sign of low refrigerant level in the sealed system. Most of the refrigerant leaks are on the evaporator coil because this part experienced temperature changes multiple time during the day. It also frosts and defrosts multiple times a day. All this creates a corrosion on the evaporator coil and as a result, it has freon leaks on it.
Before offering evaporator replacement to the customer I always visually check the condition of the loop heater under the unit. Because freon leaks on this part are also the common problem. The loop heater was visually OK.
I quoted to the customer for replacement of evaporator coil, dryer filter, and freon recharge. This is common repair for Sub Zero refrigerators, because of that, I have 6 different types of evaporator coils in my van. This allows me to provide same day service to my customers.
So I got my permission for repair and here are the steps I went through during the repair.
First I removed all shelves, light covers and back panel. This gives me full access to the evaporator coil.
Second I disconnected the temperature sensor. I cut the old coil and welded a new one instead. Also, I hooked up the temperature sensor to the new evaporator coil.
Third I cut an old dryer filter and welded a new one. I always replace the filter than recharge the system with the freon. This dryer filter catches lots of moister and internal particles in the freon and can be clogged also. Clogged dryer filter can be the reason for the sealed system to stop producing the cold.
Fourth I recharged the sealed system with the right amount of the freon specified in the documentation which comes with the new coils. Because the new evaporator coils are made from aluminum and not copper as old ones, they have different capacity and required the different amount of the refrigerant.
Fifth I install back wall, panes and all shelves back to the unit. Also, I cleaned the condenser coil and drain tube as a part of maintenance for Sub Zero units.
Another happy customer!
