Sub-Zero Freezer Not Working? How to Fix It

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Fred's Appliance
February 3, 2025
Refrigerator Repair

Nobody wants melted ice cream or food spoiling faster than it should just because their freezer isn’t working properly. If you’re dealing with this issue with your Sub-Zero freezer right now, we understand how frustrating it can be.

But don’t worry—it’s often possible to fix a freezer that’s acting up all on your own. There’s no need to call an expert unless there’s something seriously wrong with your appliance.

In this article, we’ll guide you through some simple step-by-step instructions to get your Sub-Zero freezer working again. We’ll only suggest calling in a professional if it’s truly necessary!

Here are five reasons why your Sub-Zero freezer isn’t working and how to fix it.

1. The Door Looks Closed, But It’s Not

It’s easy to push a refrigerator door closed and assume it’s shut all the way, only to notice later that it’s still open by an inch or so—it just needed that extra little nudge! Or maybe an item inside the freezer is sticking out and stopping it from closing properly.

When the freezer door—or drawer, on some models—is accidentally left ajar like this, all the cold air rushes out, and the temperature rises significantly, especially if it’s left open for a while.

The solution? Make sure the door is closing all the way—or better yet, turn on the freezer’s door alarm so it can beep to remind you when it’s not. Also, check for and rearrange any items that might be blocking the door.

2. It’s Time To Clean or Replace the Gasket

There’s another way cold air can escape from your Sub-Zero freezer—similar to when the door is left ajar—and that’s when you’ve got a bad gasket.

A worn or grimy freezer door gasket can create gaps in the seal, meaning it’s no longer airtight. A quick visual check should give you some clues, or you can place a flashlight inside the freezer, turn off the kitchen lights, and see if any light escapes.

If cleaning the gasket with a sponge and warm, soapy water doesn’t fix the issue, you can replace a faulty Sub-Zero freezer gasket by following these steps:

  1. Order a new gasket that’s compatible with your Sub-Zero refrigerator or freezer model.
  2. Open the freezer door or drawer (depending on your model).
  3. Remove the old gasket. Start at one corner and carefully pull it out from the metal channels or retaining strips. If it’s held in place with screws, loosen them on the retaining plates without fully removing them.
  4. Warm the new gasket with a hairdryer to soften the rubber and make it easier to install. Don’t overheat it, though.
  5. Install the new gasket. Start at one corner of the door or drawer, sliding the lip of the gasket into place along the perimeter. Make sure it fits snugly into the metal channels or retaining strips, and tighten any screws as needed.

3. The Freezer Temperature Isn’t Set Right

Here’s a quick and simple fix that’s easy to overlook: if the temperature settings are too warm, your freezer might be, well, too warm.

For Sub-Zero refrigerators or standalone freezers with a temperature dial, the freezer temperature should usually be set between 4 and 6. Keep in mind, 1 is the warmest, and 10 is the coldest.

If you’ve got an electronic control panel, it’s generally recommended to set the freezer temperature to 0°F (-18°C).

4. The Condenser Coils Need a Good Cleaning

If it’s been more than three months since the condenser coils were last cleaned, it’s probably time to give them a good clean to get your appliance working efficiently again (unless your fridge is less than six months old). When the condenser coils are clogged with dust, dirt, and hair, the freezer can struggle to maintain the right temperature because it disrupts the refrigeration cycle.

If it’s been a while since the coils were cleaned, here’s how to do it effectively:

  1. Unplug your Sub-Zero refrigerator.
  2. Remove the grille at the top of the appliance.
  3. Use a vacuum with a hose attachment and a brush to gently clean the coils.
  4. Remember to clean them every few months going forward!

5. Excessive Ice Buildup on the Evaporator Coils

Another reason your Sub-Zero freezer might not be cooling properly is that the evaporator coils could be frozen over, stopping cold air from circulating around the unit. You can check if this is the case by:

  • Unplugging the refrigerator or freezer.
  • Taking off the back panel inside the freezer section (it’s usually held in place with screws).

If, when you take a look, you see the evaporator coils covered in a thick layer of ice (a thin layer of frost is normal), then this is likely the issue. The coils freezing over is often caused by a problem with the defrost timer, defrost heater, door gasket, or vents. You’ll need to fix the root cause to stop this from happening again.

Since we’ve already covered how to troubleshoot the door gasket, here’s how to look into the other possible causes:

Defrost timer

The defrost timer is usually located near the condenser on Sub-Zero refrigerators. Remove the screws, disconnect its wire harness, and take it out. Use a multimeter to test it in cooling mode by placing the probes on pins 1 and 4. You should get a continuity reading of 10 to 150 ohms. If not, the timer is faulty. Next, turn the timer dial to defrost mode and check for continuity between pins 1 and 2. If there’s no reading, the timer needs replacing.

Defrost heater

The defrost heater in a Sub-Zero refrigerator is located near the evaporator coils. Start by disconnecting the wires from the heater terminals. Then, place the multimeter probes on the terminals. A working defrost heater should give you a reading of around 10 to 150 ohms. If there’s no continuity (the multimeter doesn’t beep or show any reading), the heater is faulty and needs to be replaced.

Vents

If the vents inside the freezer are blocked—either by frost buildup or because the freezer is overstuffed with food—it can mess with the cold air circulation. This can stop the freezer from freezing properly, as the cold air gets trapped around the evaporator coils, causing them to ice up. To fix this, check the vents to make sure they’re not blocked or frozen over, and if the freezer is packed too full, take out some items to improve airflow.

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