[gerryC]

Thawed the condencer.

Have sent mom out to get new freezer fan.,

To save another 40mi round trip should I have her also get another defrost thermostat and timer?

subzero is 20 yrs old

[woodchuck]

The freezer fan won't cause the coils to ice up. A defective defrost system will. You can check the defrost timer, defrost heater and defrost thermostat here.>>Refrigerator Repair Guide: How To Fix a Refrigerator - ACME HOW TO.com

Sorry I didn't catch your mother before she left.

[gerryC]

Replaced fan--freezer working normal, defrost cycle works, no freeze up 16 hrs later

another issue--refer side only drops to 45^ at highest setting on subzero

will check Acme--thanks for the post and web site

gerry:

[gerryC]

Refer deftost timer is working, replaced defective temp controller.
Refer still will not go below 48^ Cannot locate defrost thermocouple on SubZero
model 3211rfd;
Top 3 lines on the refer coils are frosted up, bottom coils are cold. Is this normal

Also, freezer is not frosting up--so is the defrost system working normal?

[woodchuck]

An irregular frost pattern is a sign of low freon. What you describe is irregular as opposed to even frosting on all the coils. Are the three lines that are frosted, in your freezer. The defrost thermostat is clamped to the coils in the freezer, usually at the top.

[gerryC]

The coils that have frost are in the refer. The entire back of the refer is a coil--there are about 12-15 lines in a serpentine pattern across the entire back of the refer. the refer temp control line is attached to the top coil(is newly replaced)

Also, I see no passage for air between the freezer and the refer. They appear to be independent.

Your reference to the freezer coil--is this the one with the fins, like a car radiator. This is located in the top of the freezer(freezer working normal) Also testing the defrost timer shows normal behavior.

[gerryC]

finally found defrost tc and it is defective.

But I still don't understand why freezer is now operating normal after fan replace and the refer is having the defrost issue?

[woodchuck]

Ok I was just doing some reading and now realize that you have two separate systems. So I assume the defrost for the fridge side is separate as is the sealed system. The symptoms for low freon and defrost issues will be the same. I can't get a diagram with your model #. Check it and I'll try again.

[gerryC]

I also got a reply from the subzero tech support:

Defrost system is for freezer only. Refer defrost via a temp control attached to the refer coils and from the warming air in the refer.

I did get a schematic from one of the refer parts web sites that showed the
defrost components in the refer side--not as it is in the freezer side. It also showed a damper control system that doesn't exist.

SubZero also said it is most likely low freon due to the unequal frost build up as you said.

I will replace the defrost thermostat. defrost the refer. turn everything back on and if I still get a temp issue will call service for freon check

Thanks again for you help--will let you know final fix

[woodchuck]

Here's something a couple of years old I saw in another forum:



your sub zero does not have a defrost heater or bi-metal, it has an off cycle defrost, which means when the thermostat is satisfied, it shuts down. The evap fan shuts down with the compressor and will start again when the door is shut. I have run into your problem on several occasions and found the easy way to handle it is by using a heat gun where the ice build up has formed. I never had one come back on me. Other things you can look at includes moving the sensor bulb up on the evaporator. The top part of the evap is colder than the bottom. This will eliminate a longer run time. Sub Zero also came out with a different evap fan blade for this model when the condition was too cold at the bottom and too warm at the top. Part number for this blade is 3-15-045-0.