LG Refrigerator Er DS: The Defrost Sensor Reading Is Out of Range

Er DS means the defrost temperature sensor (a thermistor clipped to the evaporator tubing) is returning a resistance value that falls outside the board's lookup table range. This sensor tells the board when the evaporator surface temperature has risen high enough during defrost to confirm that frost has melted. Without a valid reading, the board cannot properly control the defrost heater's on/off timing.

How the Defrost Sensor Controls the Cycle

During a defrost cycle, the board turns on the defrost heater and monitors the defrost sensor's resistance. The sensor is an NTC thermistor — its resistance decreases as temperature rises. The board expects the evaporator temperature to rise from approximately -10 degrees F (operating) to approximately 45-50 degrees F (defrost termination point) over 15-25 minutes.

When the sensor reports 45-50 degrees F (specific resistance value for that temperature), the board terminates the defrost heater and restarts the compressor. If the sensor never reports this target (because it is broken), the board either runs the heater for the maximum safety time (40-60 minutes, risking overheating) or aborts defrost and displays Er DS.

Er DS vs. Er dH

Er DS is a sensor fault — the sensor itself gave an impossible reading (infinite or zero resistance). Er dH is a heater performance fault — the sensor is working but reports the temperature did not rise during defrost (heater is dead, thermostat is stuck, or board relay is bad). Er DS is about the thermometer being broken. Er dH is about the heater not producing heat.

However, a failed defrost sensor eventually causes the same practical outcome as Er dH — improper defrost timing leads to frost buildup on the evaporator, blocked airflow, and warming compartments.

Testing the Defrost Sensor

1. Unplug the refrigerator
2. Remove the freezer rear panel to expose the evaporator
3. Locate the defrost sensor — a small capsule or bead clipped to the evaporator tubing, usually near the top of the evaporator coil
4. Disconnect its 2-wire connector
5. Measure resistance: at evaporator temperature (approximately -10 to 0 degrees F), expect 15,000-25,000 ohms for a standard LG 5K NTC at below-freezing temperatures
6. Warm the sensor body by holding it in your hand: resistance should drop steadily and noticeably
7. If resistance is infinite (open) or near zero (shorted), the sensor has failed

The defrost sensor on LG refrigerators is often combined with a bi-metal thermal cutoff in a single assembly. If your model uses a combination sensor/cutoff, test both — the bi-metal should show continuity at low temperatures and open above approximately 150 degrees F.

Sensor Replacement

1. Unplug the refrigerator
2. Remove freezer shelves and the rear panel (4-8 screws)
3. If ice covers the sensor, defrost manually first (hair dryer on low or wait several hours with doors open)
4. Unclip the old sensor from the evaporator tubing — note exact mounting position
5. Disconnect the wire connector
6. Install the new sensor (6615JB2005A or model-specific, $8-18) in the identical position on the evaporator tubing. The clip must make firm thermal contact with the tubing
7. Reconnect wires. Reassemble panel, shelves, and contents
8. Run a forced defrost (Refrigerator + Ice Plus 8 sec, then Refrigerator until "Fd" appears) to verify the new sensor allows proper defrost termination

Parts and Cost

Why Sensor Position Matters

The defrost sensor must mount at the specific location on the evaporator tubing designated by LG. If clipped to a different tube or positioned in the wrong area, it reads a temperature that does not accurately represent the overall evaporator condition. A sensor mounted too low reads warm before the upper evaporator is fully defrosted (incomplete defrost, ice builds at top). Too high reads warm too late (heater runs longer than necessary, wasting energy and stressing the system).

When replacing the sensor, photograph the original position before removing it. The new sensor goes in the exact same clip location.

Er DS and Frost Patterns

If Er DS has been present for more than a few days, check the frost pattern on the evaporator when you remove the panel:

• Uniform frost across all coils = defrost cycle never runs (timer or board issue)
• Heavy ice at bottom only = sensor is positioned too high or heater is weak at the lower section
• Ice concentrated around the fan area = defrost runs but terminates too early (sensor reading warm prematurely)

The frost pattern helps diagnose whether the sensor failure is the primary issue or a secondary symptom of a defrost timing problem.

After Sensor Replacement: Temperature Recovery

After replacing the sensor and completing a forced defrost, allow 12-24 hours for compartment temperatures to stabilize. The freezer reaches 0 degrees F within 6-8 hours. The fridge section depends on cold air transfer from the freezer and takes longer (12-18 hours). Do not add large quantities of room-temperature food during this recovery period.

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LG refrigerator frosting up? The defrost sensor is a $8-18 part that controls the entire defrost cycle — we test and replace same-visit. Book defrost diagnosis.