Sub-Zero maintenance: what to do every year, and what to leave alone

1. Keep the condenser clean

The condenser is the coil that gets rid of the heat the refrigerator pulls out of the food compartments. On a built-in Sub-Zero it sits behind a grille at the top or bottom of the unit, depending on the model, and it pulls in room air, dust and pet hair with it.

When it clogs, the heat can’t get out. On a Sub-Zero 736TCI in a downtown Bellevue high-rise, the owner called because the refrigerator felt hot along the bottom. Behind the grille, the condenser was almost completely matted over with dust and lint. The 736TCI has two separate sealed systems, one for the refrigerator and one for the freezer, and both reject their heat through that one condenser. We read the compressor’s shell temperature (113.2 °F) and running current (0.86 A), then cleaned the coil on the spot.

Signs it needs cleaning: the area around the grille feels unusually hot, the unit seems to run all the time, or temperatures are creeping up.

How often: we clean it once a year for our maintenance customers. Homes with pets, a lot of dust, or renovation work nearby can need it more often.

If you do it yourself: turn the unit off at the breaker or its power switch first, use a soft brush and a vacuum, and brush in the direction of the fins so you don’t bend them.

2. Check the door gaskets

A gasket that doesn’t seal lets warm, humid air in all day. The unit runs longer, and frost builds up where it shouldn’t. On the same Bellevue 736TCI, we found the door gasket torn and pulling away along the hinge side, and quoted its replacement.

• Look along the whole gasket for tears, flattened spots, or sections pulling away from the door.
• Close the door on a strip of paper at several points around the door. If it slides out with no resistance, that section isn’t sealing.
• Clean the gaskets with warm water and mild soap. Food residue can keep them from sealing.

3. Change the water filter

If your Sub-Zero has an ice maker or a water dispenser, it has a water filter. Replace it on the schedule in your owner’s guide, or when the filter indicator says so. Old filters slow the water flow, which can mean small or hollow ice. If the ice maker has stopped altogether, see our Sub-Zero ice maker repair page.

4. Check the temperatures

Put an appliance thermometer in each compartment and read it the next morning. U.S. food-safety guidance is 40 °F or below in the refrigerator and 0 °F in the freezer. A unit that slowly drifts warmer is telling you something, usually one of the problems in our guide to why a built-in refrigerator runs constantly.

What to leave alone

• Anything involving refrigerant. Opening a sealed system requires EPA Section 608 certification, and it’s precise work: on a Sub-Zero BI-36UID in Seattle, the rating plate lists separate R134a charges of 3.50 oz and 5.50 oz for the two systems.
• Pulling a built-in out of its opening. Built-in units are fitted to the cabinetry. Reaching the machine compartment often means sliding it out from under the cabinets, as we did on a Sub-Zero 700BFI in Woodinville.
• Chipping ice with anything sharp. A puncture in an evaporator coil turns a defrost problem into a sealed-system repair.

What a maintenance visit looks like

The Bellevue owner signed up for annual maintenance, so the condenser gets cleaned and the unit gets checked every year, before dust builds up again. On a visit like that we clean the condenser, look at the gaskets, and read the compressor’s temperature and running current, so a developing problem shows up before it becomes a warm refrigerator. See our Sub-Zero repair page for the rest of what we do.