How do I fix error code F-DEF on a Samsung refrigerators?

1. undefined: Disconnect Main PCB connectors CN70 and CN81 from PCB 2. undefined: Measure resistance between CN70 PIN 5 and CN81 PIN 1 3. undefined: Expected resistance: 63 ohm (230V model) ±7%; for 120V model verify specification 4. undefined: 0 ohm indicates heater short circuit 5. undefined: Infinite ohm indicates open wire, bimetal open, or blown thermal fuse 6. undefined: Check bimetal thermostat continuity at room temperature (should be closed/0Ω below 40°C) 7. undefined: Check thermal fuse continuity (should be 0Ω if fuse has not blown)

Samsung Refrigerators2022–present

Error Code F-DEF

Freezer defrost heater or safety cutout has failed or wiring is open

Moderate

Address soon - your appliance may not work properly

Also displayed as: F-DEF Er

What This Means

Defrost heater wire disconnected at CN70 or CN81; Bimetal thermostat (off at 60°C / on at 40°C) is open; Thermal fuse (109/110°C) is blown; Defrost heater element open circuit

What actually causes this:

The heater that melts frost off the freezer evaporator coils has stopped working, usually because the thermal fuse has blown or the heater element itself has burned out.

First Thing to Check

After unplugging the unit, measure resistance between the heater wires — if you get infinite resistance, either the heater or the thermal fuse has blown.

Parts Involved

Freezer defrost heater (AC 120V 230W)Bimetal thermostat (off 60°C / on 40°C)Thermal fuse (109/110°C)Main PCB connectors CN70 and CN81

How to Fix

1
Disconnect Main PCB connectors CN70 and CN81 from PCB
2
Measure resistance between CN70 PIN 5 and CN81 PIN 1
3
Expected resistance: 63 ohm (230V model) ±7%; for 120V model verify specification
4
0 ohm indicates heater short circuit
5
Infinite ohm indicates open wire, bimetal open, or blown thermal fuse
6
Check bimetal thermostat continuity at room temperature (should be closed/0Ω below 40°C)
7
Check thermal fuse continuity (should be 0Ω if fuse has not blown)