Troubleshooting Frost-Free Refrigerators

Written by Ian Kelly; Updated December 06, 2018. Moisture in the air collects on cold surfaces inside the freezer, forming frost. Frost, or ice, is an effective insulator as shown by igloos designed to keep Eskimos warm during Arctic winters. This insulating ice layer impairs refrigerator performance and can be caused by several factors. These include a defective door seal that allows moist air to settle on cold freezer walls or a faulty component interrupting the built-in automatic defrost cycle. Consequently, when troubleshooting frost-free refrigerators, you need to ensure that all relevant components are in working order.

Door Seals

Inspect both the freezer and refrigerator door seals carefully. Close both doors and inspect all four sides of the seal to ensure that it is compressed and making full contact with the sides of the refrigerator. Open the doors and inspect the rubber surfaces carefully. If you detect any cracks or signs of wear, replace both door seals.

Evaporator Fan

The evaporator fan built into the back wall of your freezer blows cold air from the freezer compartment into the fresh food section of the refrigerator via a duct attached to the back wall. This duct is designed to accept cold air from the freezer and to return slightly warm air from the fresh food compartment back into the freezer to allow it to remove the heat contained in the warmer air. The defrost thermostat controls power to both the evaporator fan and the compressor by turning them on or off in conjunction with the defrost cycle. You can tell if the fan is working by either listening to it or by holding your hand over the cold air outlet in the refrigerator section. If the fan does not work while the compressor is running, it has burned out and must be replaced.

Duct

The duct leading from the freezer compartment to the refrigerator fresh food compartment can become blocked with ice buildup. The duct also contains a movable diffuser flap that allows warmer air back into the freezer compartment. Remove the screws securing the duct and make sure that it isn’t blocked with ice and that the diffuser flap is moving freely. Then reinstall the duct, close the door and allow the refrigerator to cool down. As soon as the compressor starts, open the door, hold your hand over cold air outlet, and feel if cold air is blowing out of the duct.

Mechanical Defrost Timer

For this diagnosis to work, the freezer must be frozen down or the evaporator must be encrusted with ice. Expose the evaporator coil as follows: Unplug the refrigerator. Remove the upper and lower panels from the back wall of the freezer compartment and the refrigerator section if you have a single door refrigerator. If you have a double-door unit, remove the back panel from the freezer section. Plug the refrigerator back in. Locate the defrost timer inside the refrigerator compartment; you will see a slotted screw with a pointer. Insert a screwdriver into the slot and turn the timer screw so that the pointer is opposite the defrost mode. At this point, the refrigerator will stop working. Locate the defrost heater mounted on or behind the bottom of the evaporator coil. Wait about five minutes. If the defrost heater is working, it will glow red and start melting the ice on the evaporator coil. If it fails to heat up, either the defrost timer is broken or the heater is bad and must be replaced.

Defrost Heater

Unplug the refrigerator before carrying out this test. Locate the thermostat clipped onto a freezer coil on the top of the evaporator. Disconnect the plug or spade connectors leading from the evaporator heater to the thermostat. Set your digital or analog multitester to the lowest ohms of resistance mode; if you’re using an analog meter, turn the adjusting knob on the side of the meter until the needle points to zero. Watch the readout. Insert the red probe into one of the terminals leading from the heater and the black probe into the other terminal. If the readout shows a resistance between zero and 50 ohms, the heater is good. If the readout doesn’t move, the heater is faulty and must be replaced.

Thermostat

With the refrigerator unplugged, open the doors and allow the interior to warm up to 30 degrees Fahrenheit or above. Unclip the thermostat from the freezer coil on the evaporator and unplug the spade connectors. Place the thermostat in a glass of cold water containing ice cubes for two or three minutes. This will allow the bimetal contacts inside the thermostat to flex and make contact with each other. Set the multimeter to the lowest ohms of resistance mode as described previously. Touch the red probe to one of the terminals and the black probe into the other terminal while watching the readout. If the readout shows zero ohms of resistance, the thermostat has continuity and is in working order. If the readout does not change significantly, the thermostat is bad and must be replaced.

Electronic Defrost Timer

If your refrigerator is fitted with an electronic defrost timer and all of the previously described components are in working order, the timer is faulty and must be replaced. Testing a programmed electronic defrost timer requires professional expertise; however, this component is relatively inexpensive; therefore bypassing the test is usually your best choice.

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Are Sub-Zero Refrigerators Worth the Money?

Are Sub-Zero Refrigerators Worth the Money?

If you’ve ever looked into Sub-Zero refrigerators you’re aware that they are not cheap. Base prices start around $7,000 and only go up from there. Certainly they market themselves as as premium appliance for commercial applications and high end kitchens. But are they really worth the price tag? We here at Appliance Doctor, an appliance repair company serving Greater Philadelphia, work on these units fairly frequently. What follows is our take on the value you get for your dollar.

Innovative Design

Sub-Zero was the first appliance manufacturer to build and market a counter depth refrigerator. These are shallower than normal refrigerators, designed so they don’t stick out a distance into your kitchen the way normal fridges do. This sort of innovative thinking is a hallmark of the company.

They are currently the leading manufacturer of integrated refrigeration units. These appliances take the counter depth model to its logical conclusion, replacing the normal fridge door with panels exactly matched to your kitchen cabinets. With a quality unit when it’s closed you can’t tell it’s there. It looks just like a bank of cabinets. If this sort of integrated look is something you like Sub-Zero is a good choice.

Dual Compressors

This was unique to Sub-Zero refrigerators until recently, but as the innovator of the technology Sub-Zero’s designs are arguably better. Most refrigerators have a single compressor for the fridge and freezer portions of the appliance. The problem with this is that the moist air in the fridge mingles with the dry air in the freezer, which can lead to frost problems, particularly if the auto-defrost function in the freezer isn’t working properly. It also tends to migrate strong smells from the fridge into the freezer, which can taint your ice and other items.

Having two compressors, one for the fridge and second for the freezer is much better. With that design no air every crosses between the two halves of the unit.

Integrated Air Purification

Sub-Zero refrigerators include air purifiers that cleanse the air of mold spores, germs, viruses and the gasses given off by spoiling food. This helps keep food fresher longer and prevents that unpleasant moment when you open the fridge and encounter the nasty smell of rotting food.

Active Vacuum Seal

Unlike normal refrigerators, Sub-Zero fridges employ an active vacuum seal to prevent outside air from entering the fridge interior. This works in concert with the air purifiers to extend the life of your food.

Thoroughly Tested

In any given run of refrigerators it’s common for the factory to only test a few units as representatives of the rest, the logic holding that if those are built properly the rest should be, too. By comparison Sub-Zero thoroughly tests each and every unit before it’s shipped. This guarantees that your appliance is built well and functions properly, every-time.

So Are They Worth It?

Sub-Zero is certainly one of the best refrigerators money can buy. Whether they’re right for you, though, is something of a personal question. If you can afford the hefty price tag then by all means put one in your kitchen. Otherwise, consider how long you’ll be in your home. If this is your dream kitchen and you’ll be using it for years, the price may be worth it. Because of Sub-Zero’s quality and name recognition, the appliances feature great resale value. Should you ever sell your home being able to advertise a Sub-Zero fridge could help bring in buyers.

Sub-Zero refrigerators have an excellent performance record, but if you ever do need repairs we can help. We’re an appliance repair company serving Greater Philadelphia, so we can be there quickly to give your refrigerator the TLC it needs.

Are Sub-Zero Refrigerators Worth the Money?

Appliance Doctor, Incorporated is a Pennsylvania Corporation offering expert repair services to the Delaware Valley’s residents and businesses. We started in 1964 as a one-man business servicing only washers and dryers. Today, we service more than 110 different brands of refrigeration and appliance equipment across 49 different product types. Our technicians are expected to know so much information! In the 1960’s, our service area was limited to Philadelphia. Today, our service area includes all towns in Philadelphia, Bucks County, Montgomery County, Delaware County, and Chester County.