Quick Answer
A freezer that is not freezing has lost the ability to circulate adequate cold to the compartment. The most common single cause in units five to fifteen years old is frozen evaporator coils — a thick layer of ice that accumulates when the defrost system fails to clear frost off the coils, blocking cold air entirely. If both compartments (freezer and fresh-food) are warm simultaneously, the compressor has likely failed or refrigerant pressure is critically low. If only the freezer is warm while the refrigerator stays cool, the fault is more likely airflow, defrost cycle, or evaporator-specific.
Common Causes
Frozen Evaporator Coils: The evaporator coils behind the freezer wall panel are where refrigerant absorbs heat and produces cold. The defrost system runs automatically every 6–12 hours to melt frost that accumulates on these coils. When the defrost thermostat, defrost heater, or defrost timer fails, frost accumulates unchecked. Over days, a thick ice layer forms that completely blocks cold air from entering the compartment — the freezer warms up while the refrigerator may paradoxically overcool. This is the most common cause of a failing freezer in units in the 5–15 year age range.
Failed Compressor: The compressor is the pump that circulates refrigerant through the entire cooling system. A compressor that has failed completely produces no cold in either compartment. One that is struggling may produce weak cooling — the freezer reaches only 20–30°F instead of 0°F. Compressor failure is often preceded by warning signs: a buzzing or grinding noise from the lower rear of the unit, the motor cycling on and off repeatedly, or the compressor running continuously without the temperature dropping.
Defrost Thermostat or Heater Failure: The defrost cycle relies on a thermostat to sense coil temperature and signal the defrost heater to activate. If either component fails — the thermostat reading incorrectly or the heater element burning out — the coils ice over without interruption. The result is identical to a blocked evaporator: cold air cannot flow from the coils to the compartment.
Airflow Blockage in Vents: Cold air produced at the evaporator coils is distributed to both compartments through insulated ducts and vents. Food packages pushed against these vent openings, ice buildup in the duct, or debris partially obstructing the fan can reduce or completely stop cold air from reaching the freezer. A partially blocked vent may show as moderately elevated freezer temperature; a fully blocked vent prevents any cold air circulation to that zone.
Low Refrigerant from a Leak: A refrigerant leak — from a cracked line, corroded fitting, or failed connection — causes the system to gradually lose cooling capacity over days or weeks. Both compartments warm slowly as refrigerant levels drop. Refrigerant leaks cannot be corrected by simply adding refrigerant; the leak source must be found, sealed, the system evacuated, and refrigerant recharged to specification.
Failed Expansion Valve or Capillary Tube: The expansion valve meters refrigerant into the evaporator coils. If it sticks closed or clogs, insufficient refrigerant flows to the coils, producing weak or absent cooling in both compartments — a symptom similar to low refrigerant but without an actual leak.
Checks You Can Do Yourself
Check both compartments: Measure or estimate the temperature of both the freezer and fresh-food sections. If only the freezer is warm while the refrigerator is cool or normal, the problem is likely compartment-specific — airflow, defrost system, or evaporator. If both sections are warm simultaneously, the compressor or refrigerant circuit is the likely fault.
Listen for motor activity: With the unit running, place a hand on the back exterior wall (condenser area) or listen near the lower rear. A functioning compressor produces a low, steady hum and the condenser area will feel slightly warm. Silence suggests the compressor is not running. A loud buzzing, clicking, or grinding from the compressor area indicates it is struggling to start.
Check for ice buildup on the evaporator wall: If the freezer has a removable rear wall panel, remove it and look at the evaporator coils behind it. A thin rime of frost is normal. A solid block of ice covering the coils entirely indicates the defrost system has failed. If you see this, the immediate fix is to unplug the unit and allow the ice to melt — but the underlying defrost component failure will need to be identified and repaired or the ice will reaccumulate.
Inspect the freezer vents: Look inside the freezer compartment for the small vent openings that deliver cold air from the evaporator. Make sure no food packages are blocking them. Move any items obstructing vents and wait 2–4 hours. If temperature improves, airflow obstruction was a contributing factor.
Check the defrost drain: A clogged defrost drain can cause ice to back up into the evaporator area. Locate the drain opening — typically a small hole at the rear bottom of the freezer interior — and check whether it is blocked with ice. Flushing with warm water can clear a blocked drain, but will not repair a failed defrost thermostat or heater causing the ice formation.
What NOT to Do
Do not attempt to recharge refrigerant yourself. Refrigerant is pressurized and requires EPA certification and specialized equipment to handle safely. DIY refill kits do not address the leak that caused the loss and can overpressurize the system.
Do not use a heat gun or hair dryer to melt ice off frozen evaporator coils. Rapid heat can crack plastic duct components and damage the coil tubing. Allow ice to melt naturally with the unit unplugged, or wait for a technician to perform a controlled defrost.
Do not force or pry open refrigerant lines or compressor connections. This releases refrigerant — an ozone-depleting substance in older systems — and creates a potentially dangerous pressurized leak.
Do not continue running a unit with a loudly buzzing or grinding compressor. Prolonged operation with a failing compressor can cause internal mechanical damage that extends beyond the compressor itself.
When to Call a Professional
If both compartments are warm, if clearing vent blockages and allowing the unit to defrost does not restore freezer temperature, or if the compressor is making abnormal sounds — professional diagnosis is required. Compressor testing, refrigerant pressure measurement, and defrost component continuity testing each require specialized tools and training. A weak compressor and low refrigerant from a leak both present similar symptoms but require entirely different repairs.
Food safety is also a factor: if the freezer has been above 40°F for more than two hours, perishable items should be relocated. Schedule repair promptly to avoid the loss accelerating further.
What a Technician Evaluates
A technician begins by testing the compressor — confirming it is running and checking refrigerant pressure with a manifold gauge set. Normal pressure confirms the refrigerant circuit is intact and redirects attention to the defrost system or airflow. Low or absent pressure points to a refrigerant leak or compressor failure, both of which require further isolation to identify the specific fault.
The evaporator coils are inspected for frost or ice accumulation. If the coils are iced over, the defrost circuit components are individually tested: the defrost thermostat is checked for continuity at low temperature, the defrost heater element is tested for resistance, and the defrost timer or control board is verified for correct cycle timing. Whichever component fails its test is replaced. Airflow through the evaporator fan and duct vents is also confirmed. After repairs, the technician runs the unit through a complete cooling and defrost cycle to verify the freezer reaches and holds the target temperature before completing the visit.
Frequently Asked Questions
If my freezer is warm, is the compressor definitely dead? Not necessarily. A weak compressor, a clogged expansion valve, low refrigerant, frozen evaporator coils, or a blocked vent can all produce the same symptom. Professional testing with a refrigerant pressure gauge and component continuity checks is needed to distinguish between these causes.
Can frozen evaporator coils thaw on their own? Yes, if the unit is unplugged for several hours, the ice will melt. However, if the defrost thermostat or heater has failed, the ice will begin accumulating again immediately once the unit is restarted. Unplugging resolves the symptom temporarily but does not repair the underlying defrost system fault.
Will leaving the freezer door open help it get colder? No. Leaving the door open prevents the thermostat from ending the cooling cycle, which can strain the compressor and introduce warm, humid air that worsens frost accumulation once the door is closed again.
Is it safe to keep food in a warming freezer while waiting for repair? Only briefly. Perishable food at temperatures above 40°F for more than two hours is at elevated safety risk. Relocate frozen items to a working freezer or a cooler with ice, and schedule repair as soon as possible.
Why does my freezer ice up quickly now when it didn't before? Aging defrost system components — the thermostat or heater element — may be degrading, causing defrost cycles to run incompletely or not at all. A door gasket that has lost its seal can also allow humid air in, accelerating frost formation independent of the defrost system.
Can adjusting the thermostat dial fix a freezer that isn't freezing? Adjusting the dial may help if the thermostat is slightly miscalibrated, but it will not correct mechanical failures like iced-over coils or a weak compressor. If turning the dial has no observable effect on temperature after several hours, the problem is mechanical rather than a calibration issue.
Other refrigerator issues? See the guide on refrigerator not cooling or fridge leaking water. For a full overview, visit the refrigerator repair resource page.
For professional repair service in Denver, see our freezer not freezing repair in Denver page. Related: refrigerator not cooling in Denver.