LG Refrigerator Thermostat Replacement — Defrost and Cold Control
LG refrigerators use different thermostat types depending on the model era and function. Modern electronic LG refrigerators regulate temperature through thermistors and the control board, but still use a mechanical defrost thermostat (bimetal) in the defrost circuit. Older models may also have a cold control thermostat for the main temperature dial.
Defrost Thermostat (Bimetal)
The defrost thermostat is a bimetal disc mounted on the evaporator coil. It closes when the coil temperature drops below a threshold (approximately 30-35F) and opens when the coil warms above approximately 50F during a defrost cycle. This switch is in series with the defrost heater — it prevents the heater from running when the coils are already warm.
When the defrost thermostat fails open, the defrost heater cannot run even when the timer or board initiates a defrost cycle. Ice accumulates on the evaporator coils until airflow is blocked, and the refrigerator stops cooling.
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Cold Control Thermostat (Older Models)
Older LG refrigerators with a manual temperature dial use a cold control thermostat — a capillary tube device similar to an oven thermostat but calibrated for refrigerator temperatures. This thermostat cycles the compressor on and off to maintain the selected temperature. Modern electronic LG refrigerators do not have this component — they use thermistors and the control board instead.
Symptoms
| Symptom | Thermostat Type |
|---|---|
| Heavy frost buildup on evaporator coils | Defrost thermostat stuck open |
| Refrigerator runs constantly, still not cold enough | Defrost thermostat (ice blocking airflow) |
| Compressor never shuts off | Cold control stuck closed (older models) |
| Compressor never starts | Cold control stuck open (older models) |
| Defrost heater runs but does not shut off | Defrost thermostat stuck closed |
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Appliances involve high voltage (120-240V), pressurized water, gas lines, and chemical refrigerants. Over 400 DIY repair injuries are reported yearly. Our techs are licensed and insured — let them handle the risk.
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Part Numbers and Pricing
| Part | LG Number | Price |
|---|---|---|
| Defrost thermostat (bimetal) | 6931JB2002Q | $10-$30 |
| Cold control thermostat (older models) | Model-specific | $15-$40 |
| Defrost heater (often replaced together) | 5300JB1092A | $20-$50 |
| Professional replacement | — | $100-$170 |
Testing the Defrost Thermostat
Disconnect power. Access the evaporator coils by removing the rear freezer panel. Locate the bimetal thermostat clipped to the evaporator — it is a small disc with two wires.
Disconnect the wires. At freezer temperature, the thermostat should show continuity (closed). At room temperature, it should show no continuity (open). If it reads open at freezer temperature, it has failed and must be replaced.
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Replacement
The defrost thermostat clips onto the evaporator coil tube. Unclip it, disconnect the wires, clip the new one on, reconnect. Reassemble the freezer panel.
If replacing the defrost thermostat due to ice buildup, fully defrost the unit first (unplug for 24 hours with doors open). Also test the defrost heater and defrost timer/board — the thermostat is just one component in the defrost circuit.
The Complete Defrost Circuit
The defrost system has three components working together: the defrost timer or board (initiates defrost), the defrost heater (melts ice), and the defrost thermostat (opens the heater circuit when coils are warm enough). If ice is building up, any one of these three could have failed. Test all three before ordering parts.
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Frequently Asked Questions
My LG refrigerator has ice all over the back wall of the freezer. Is the thermostat bad?
Possibly — the defrost thermostat, heater, or timer/board has failed, preventing defrost cycles. Test all three components. The thermostat ($10-$30) is the cheapest to replace.
My older LG refrigerator compressor runs non-stop. Is it the cold control?
If the cold control thermostat is stuck closed, it keeps the compressor running continuously. Turn the temperature dial — if the compressor does not cycle off at any setting, the cold control has likely failed.
Can I defrost my LG refrigerator manually while waiting for parts?
Yes. Unplug the refrigerator, open both doors, and let it sit for 24 hours. Place towels to catch melt water. This is a temporary fix — the ice will return in 1-2 weeks if the defrost system is not repaired.
LG refrigerator icing up or not cycling properly? Our technicians test the complete defrost circuit. Book a technician →
