Samsung Refrigerator Not Heating? Defrost Heater
Most likely a defrost heater element has failed — Samsung uses glass-tube calrod heaters that crack from thermal cycling — so the evaporator never clears its frost. A PCB defrost relay stuck open or a failed anti-sweat mullion heater can produce the same no-heat result, so run Forced Defrost to confirm which heater is…
How Samsung defrost heating works#
Twin Cooling Plus models in the RF and RS series carry separate defrost heaters for the fridge and freezer evaporators, each operating independently. On a defrost cycle they warm the coils to melt frost so airflow stays clear. When a heater fails, frost accumulates, airflow chokes, and the compartment gradually warms even though the compressor runs — so no-heat here really means no defrost.
Causes at a glance#
| Likely cause | What you'll notice | How common | First move |
|---|---|---|---|
| Defrost heater element failed | Frost on the coil, warming section | Most common | Run Forced Defrost, test the heater |
| PCB defrost relay open | Heater never energizes on defrost | Common | Test the relay on the main PCB |
| Anti-sweat / mullion heater failed | Sweating at the door center | Occasional | Test the mullion heater |
| Thermal fuse or sensor open | Defrost blocked, sensor fault | Occasional | Check the fuse and sensor |
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Working through the causes#
Defrost heater element failed (most common). Samsung uses glass-tube calrod heaters, and the swing from freezing to 140°F and above every defrost cycle fatigues the glass until it cracks and the element goes open. With the heater dead, frost keeps building on the evaporator. The defrost heater, such as part DA47-00244W on many RF and RS models, is tested for continuity and replaced. PCB defrost relay open (common). The main PCB switches power to the defrost heaters through relays. If a relay fails open, the heater never receives power even though the element itself is fine. The relay on the PCB (board family around DA92-00384B) is tested, and the board is replaced if the relay has failed. Anti-sweat / mullion heater failed (occasional). Thin wire heaters in the door frame and center mullion keep those surfaces above the dew point. When one fails, that area sweats even though the cooling is normal. The mullion heater is tested and replaced. Thermal fuse or sensor open (occasional). A blown defrost thermal fuse or a failed defrost sensor can stop the defrost circuit from energizing the heater at all. Both are checked when a known-good heater still will not run.
Confirm it with Forced Defrost#
- Disconnect power at the breaker before any internal inspection.
- Restore power and enter Forced Defrost: hold the Lighting and Fridge buttons together for about 8 seconds until the display shows Fd.
- Both defrost heaters should energize; listen and feel for warming at the evaporator.
- A heater that never warms is either open or not receiving power from the PCB.
- Test the suspect heater for continuity to separate a dead element from a relay or fuse fault.
Safety First — Know the Risks
Refrigerant (R-134a/R-600a) requires EPA certification to handle. Improper discharge is a federal violation and health hazard. Our techs are licensed and insured — let them handle the risk.
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Preventing a repeat#
- Do not pack the freezer so tightly that airflow around the evaporator is blocked.
- Address early frost buildup before it chokes airflow and warms the food.
- Keep the door gaskets sealing so humid air is not constantly loading the coil.
- Have the defrost system checked if frost returns soon after a manual defrost.
- Keep the freezer door sealing so humid air does not overload the evaporator with frost.
- Do not block the vents inside the freezer, which starves airflow and hastens frost buildup.
- Replace a cracked glass-tube heater promptly, since frost only worsens while it is open.
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Senior Appliance Repair Technician · 15 years experience
EPA-certified technician with 15 years of experience specializing in refrigerator and cooling system repairs.
