Error Code F-DEF ERROR
Freezer defrost heater is not working — ice may build up on evaporator
Critical
Stop using immediately - risk of damage or safety issue
Also displayed as: F LED blinks (defrost error)
What This Means
Defrost heater open or shorted; Bimetal thermoprotector tripped or open (off at 140°F/60°C, resets at 104°F/40°C); Thermal fuse blown (109°C/228°F cutoff, one-shot non-resettable); Wiring harness disconnection
What actually causes this:
The bimetal thermoprotector trips if the heater runs too long or the defrost sensor fails to terminate defrost in time. Less commonly the heater element itself burns out.
First Thing to Check
Power off and measure the resistance across the defrost heater connections — if you get infinite resistance (open circuit), the heater, bimetal, or thermal fuse has failed.
Parts Involved
How to Fix
- 1
Run self-diagnostic function to confirm F-DEF error
- 2
Power off the unit; disconnect CN20 from Main PCB
- 3
Measure resistance between CN20-6 and CN20-8: expected 63 Ω ±7% (120V) or 230 Ω ±7% (230V)
- 4
0 Ω indicates heater short; infinite Ω indicates wire or bimetal open
- 5
Check defrost sensor — at 86°F (30°C) should be 4.22 kΩ; at 32°F (0°C) should be 13.29 kΩ
- 6
Initiate forced defrost (Fd) mode to verify heater activates and system returns to cooling when defrost sensor reaches 50°F (10°C)/53.6°F (12°C)
This Error Applies To
Samsung RF27T5 Series Refrigerators (2020) (2020–present)
Related Error Codes
Refrigerator compartment temperature sensor failed or disconnected
Freezer temperature sensor has failed or disconnected
Freezer fan motor is not spinning or not sending a rotation signal
Condenser fan in the machine compartment is not spinning
The compressor inverter power module has detected a fault and shut down