Error Code F DEF ERROR
Freezer defrost heater or associated protection device has failed
Critical
Stop using immediately - risk of damage or safety issue
Also displayed as: F DEF ERROR on self-diagnosis
What This Means
Defrost heater open circuit (burned out); Bimetal thermo protector tripped open (Off at 140F/60C, resets at 104F/40C); Thermal fuse blown (109C/228F, 250V 15A, one-shot non-resettable); Bad wiring connection at heater; Relay failure on PCB
What actually causes this:
Heater burned out from age or repeated cycling; thermal fuse blown from over-temperature event; bimetal stuck open
First Thing to Check
With CN20 disconnected, measure resistance at CN20 pins 6 to 8; 0 ohm means short, infinite ohm means open
Parts Involved
How to Fix
- 1
Select self-diagnosis function; check for F DEF error code before power off
- 2
Disconnect CN20 from PCB; measure resistance between CN20 pin 6 and pin 8 — expect 63 ohm plus or minus 7% at 120V or 230 ohm plus or minus 7% at 230V
- 3
0 ohm = heater short; infinite ohm = heater/bimetal/thermal fuse open
- 4
Confirm defrost sensor temperature is below 53.6F (12C) before expecting heater activation
- 5
Run Force Defrost (Fd) mode; confirm system returns to cooling after defrost completes
- 6
Check relay for proper switching if heater circuit is intact but defrost does not run
This Error Applies To
Samsung RF28T5F Series Refrigerators (2020) (2020–present)