Freezer Ice Building Up

Freezer Ice Building Up

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If there is a buildup of frost, ice, snow, and frozen water in all its forms on the back wall, you're on the right page. If you are more specifically talking about an ice maker that won't stop making ice, follow the fixes on the ice maker problem page.

Occasionally, you will need to defrost your freezer. If you're needing to defrost more than once a year, then follow the fixes below.


Before removing and replacing or continuity testing electrical components, power down the fridge. This will prevent damage to the components and prevent you from being electrocuted.

  • If the fridge is pulled away from the wall, remove the plug.
  • Otherwise, find the fridge’s circuit breaker in your breaker box and turn the circuit off.
  • Check that the lights are off in in the fridge when you open the door

When working around the evaporator, consider wearing gloves to avoid cuts from the sharp sheet metal. The fins are very thin in many cases and can give very bad cuts.



Ice buildup happens when warm and humid air contacts cold evaporator coils in the freezer. This moisture is frozen and quickly forms into a wall of ice. By ensuring food is at room temperature before being placed into freezer containers you will avoid releasing warm air in the freezer.


The evaporator fan blows air cold around the freezer. And while the freezer is more efficient when it is appropriately loaded with food. Too much food or incorrectly placed food will block the vents and prevent proper temperature regulation. The refrigerator vents allow for airflow between the fridge and freezer compartments. Blocking these vents may result in many issues.

  • Locate your evaporator fan and move frozen items further away.
  • Unblock the vents. A rule of thumb for frost prevention is to stock enough food to fill the freezer while keeping an inch of space between the food and the walls.

When the freezer door is opened, warm and humid air will enter and cause ice to form. This is inevitable, though it can be minimized by reducing the time spent searching for food. You may experience this issue more during humid summers than dry winters.


If your fridge door has a built-in ice dispenser, inspect the chute door for a stuck ice cube or piece. If the chute door is open, warm air can slowly seep into the freezer compartment.

  • Remove any blockages.

Door seals are gaskets for your fridge, and as they age and fall apart, cool air escapes through the cracks in door seals.


If the evaporator cover in your freezer is covered in ice crystals, or otherwise frozen over, there's an issue with your defrost system.

Defrost Type

Frost-free appliances regulate temperature to prevent ice build-up. Automatic and adaptive defrost systems prevent and remove ice build-up by circulating heat as needed; automatic systems typically run on a timer, while adaptive systems use sensors to determine when to circulate the heat.

Initial Troubleshooting

The most modern freezers have an auto-defrost system. This defrost system has four main parts: a defrost heater, a bi-metal thermostat, an electronic control board, and a thermistor. Let's begin troubleshooting the defrost heater system.

  • Test to see if the defrost heater works. Put your freezer into forced defrost mode. On some models this mode is entered by pushing the door sensor 5 times in 2 seconds. The controller will beep and the defrost mode will start. This mode can be exited by unplugging the fridge.
    • If this procedure doesn't work, check the tech sheet located under or behind your fridge for your specific procedures.
  • Check to see if the heater heats up.
    • If it heats up, jump to the thermistor section.
    • If it doesn't heat up, begin troubleshooting the system starting with the defrost heater.

Like a fuse blowing from an overload, your thermal fuse may blow when your defrost system overheats. One sign that your fuse may have blown is your evaporator freezing over.

  • Continuity test your fuse and replace it if the reading is more than 1Ω

The defrost heater melts frost off the evaporator fins. If the defrost heater fails, the frost stays put, and the entire evaporator eventually becomes ice.

Block Image
  • Locate the defrost heater. If you notice any bumps or cracks, replace it immediately.
  • Continuity test the heater. A resistance value outside 50-120Ω will need to be replaced with a new unit.

The defrost timer initiates 30-minute heating cycles every 8-10 hours of fridge run time. If this unit fails, your fridge will be stuck in either the heating or cooling cycle. It's time to test the defrost timer.

  • In units with an adaptive defrost control board, you'll have to enable the defrost cycle manually.
    • For some models turn the thermostat off for 15 seconds, then on for 5 seconds. Repeat this two more times, then turn the thermostat off.
    • The defrost cycle should be turned on. Test the temperature with a thermometer to see if your fridge is heating up.
  • With a manual timer, test between terminals 1 and 4 for continuity.
    • Continuity here means that the cooling cycle is operating.
  • Rotate the manual dial until hearing a click. Now test between pins 1 and 2 for continuity. This means that the heating cycle is working, and there should be no continuity between pins 1 and 4.
  • If continuity tests fail or the fridge doesn't enter defrost mode, replace the timer with a new one.

Another problem that prevents your fridge from getting cold enough is a faulty thermistor. The thermistor is a sensor that monitors temperature. It is connected to the control board. If a thermistor is defective, the refrigerator may not cool (or may cool continuously). This is not likely if the compressor is running but the unit is not cooling.

There may be up to four thermistors on your fridge:

  • The fresh food compartment thermistor
  • The fresh food defrost thermistor
  • The freezer compartment thermistor
  • The freezer defrost thermistor

The compartment thermistors sense the air temperature in the compartment they are placed in. The defrost thermistors sense the evaporator temperature during a defrost cycle and prevent the defrost heater from overheating the evaporator. Since many refrigerators have evaporators in both the freezer and fresh food sections, you can end up with four (or even five if the unit has an ambient air thermistor)

Block Image

Grab a multimeter and continuity test the thermistor. Place the thermistor tip into a cup of ice water made from ice, water (just enough to cover the ice), and salt. You will need to find information on the resistance value expected for your refrigerator's various thermistors at 32°F (0°C).

Another possible cause is the defrost thermistor. This can keep the defrost cycle from running fully, allowing ice to build up, which will cause temperature problems in the refrigerator either because the evaporator in the freezer frosts up or because the fresh food compartment defrost is failing in a dual evaporator system.

If the thermistors test ok go on to the next item.

Temperature Control Thermostat Failure

If the refrigerator still does not get cold enough, the temperature control thermostat (also called a bi-metal thermostat) might be faulty. The thermostat allows power to flow through to the compressor, evaporator fan, and condenser fan. If the cooling system fans and compressor are running, but the refrigerator or freezer is not cooling correctly, check for an airflow or defrost system problem.


If the refrigerator is not cold enough, the temperature control board might be defective. The temperature control board provides the voltage to the fan motors and compressor. The electronic control board starts the defrost cycle and regulates how often they are triggered. If the control fails, your fridge will not be able to defrost automatically. These boards are often misdiagnosed. Check all other components to be certain this is the cause of the problem.


In some dual evaporator style fridges, the plastic cover that covers the evaporator coils can have issues sealing. If all other components test positive in continuity and have acceptable resistance values, try replacing this part.


Finally, if the refrigerator won’t get cold enough, the main control board might be defective. This is not common. Check the defrost system, cooling fans, and cooling controls first.

Fridge Defrost Troubleshooting


Samsung Fridge Self-Diagnostic Function — View the next page in the service manual for the error code list and meanings. There are diagnostic steps for measuring the voltage and resistance of circuits.

Samsung Error Codes Troubleshooting

Samsung Ice Maker Frost Bulletin

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