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Error code reference

LG Refrigerator Error Code C1

Cycle abnormal or defective

LG codesLG refrigerator codes

Cycle abnormal or defective — compressor works for over 3 hours when FD-S or RD-S temperature is over 23°F.

First step from the service manual

Check for refrigerant leakage.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What C1 means on a LG refrigerator

The C1 error code on an LG refrigerator indicates a cycle abnormality in the cooling system. Specifically, this fault triggers when the compressor runs continuously for more than 3 hours while the temperature sensor readings at either the freezer defrost sensor (FD-S) or refrigerator defrost sensor (RD-S) remain above 23°F. Under normal operating conditions, the compressor should cycle on and off as the unit reaches target temperatures. When it cannot achieve adequate cooling and keeps running without bringing those sensor readings down to the expected range, the control board logs C1 and flags the system for diagnosis.

The most critical first step when diagnosing C1 is checking for refrigerant leakage. A refrigerant loss reduces the system's ability to transfer heat effectively, which means the compressor runs endlessly trying to compensate but never achieves the target temperatures at the defrost sensors. Beyond refrigerant loss, other potential causes include a failing compressor that cannot generate adequate pressure, a blocked or restricted refrigerant circuit, condenser coils clogged with dust and debris reducing heat dissipation, or a faulty defrost sensor providing inaccurate temperature readings to the control board.

Diagnosing C1 requires a systematic approach starting at the refrigerant circuit and working outward to electrical and sensor components. A technician should inspect all refrigerant line connections and components for oily residue, which can indicate a leak point. Condenser coil condition, compressor amperage draw, and sensor resistance values should all be evaluated before concluding which component is responsible for the prolonged compressor run time.

Source: manufacturer service documentation.

Common causes of C1

  1. 01

    Refrigerant leak

    Part replacement

    A loss of refrigerant is the primary suspect for C1. With insufficient refrigerant, the system cannot transfer heat properly, causing the compressor to run indefinitely without cooling the cabinet to target temperatures. Look for oily residue around refrigerant line connections and components as an indicator of a leak point.

  2. 02

    Dirty or blocked condenser coils

    Wiring / connection

    Heavy dust and debris buildup on the condenser coils reduces the system's ability to shed heat, forcing the compressor to run longer than normal. Inspect the coils and clean them thoroughly before moving on to more involved diagnostics.

  3. 03

    Faulty defrost sensor (FD-S or RD-S)

    Part replacement

    If the freezer defrost sensor or refrigerator defrost sensor is failing, it may report temperatures above 23°F even when the cabinet is adequately cooled, triggering a false C1 fault. Test the sensor resistance values and compare them against the expected specifications for the operating temperature.

  4. 04

    Weak or failing compressor

    Part replacement

    A compressor that cannot generate adequate pressure will run continuously without effectively circulating refrigerant through the system. Checking compressor amperage draw can help confirm whether the unit is operating within its normal working range.

  5. 05

    Restricted or blocked refrigerant circuit

    Part replacement

    A restriction in the refrigerant circuit, such as a clogged filter drier or kinked line, can reduce refrigerant flow and mimic the symptoms of a refrigerant leak. This typically requires a certified technician with refrigerant system diagnostic tools to identify and correct.

See the test procedure for each cause

Frequently asked questions about C1

What does C1 mean on a LG refrigerator?
The C1 code on an LG refrigerator means the compressor has been running continuously for more than 3 hours while the freezer defrost sensor or refrigerator defrost sensor is still reading above 23°F. This indicates the system is failing to reach its target cooling temperatures. The most common cause is a refrigerant leak, though a dirty condenser, faulty sensor, or failing compressor can also trigger this fault.
Can I fix the C1 error code on my LG refrigerator myself?
Some basic checks, such as cleaning the condenser coils or inspecting for obvious damage, can be done without professional help. However, if the root cause is a refrigerant leak, a restricted refrigerant circuit, or a failing compressor, those repairs require certified technicians with specialized equipment. Attempting to handle refrigerant yourself is illegal without EPA Section 608 certification in the United States.
Is a C1 error on my LG refrigerator a safety concern?
The C1 fault itself is not a direct safety hazard to people, but it does mean the refrigerator is not cooling properly, which puts food safety at risk. If temperatures inside the cabinet have risen into unsafe ranges for perishable items, those foods should be moved to another cold source. A refrigerant leak, if present, should be addressed promptly by a qualified technician.
Will resetting my LG refrigerator clear the C1 error code?
A power reset may temporarily clear the C1 code from the display, but the fault will return if the underlying problem is not corrected. Because the code triggers after the compressor runs for over 3 hours without adequate cooling, the same conditions will cause it to reappear quickly. Resetting without diagnosing the root cause only delays the repair and can allow food temperatures to rise further.
How much does it cost to repair a C1 error on an LG refrigerator?
Repair costs vary significantly depending on the cause. Cleaning condenser coils is inexpensive and may cost $50 to $150 if done by a technician. Sensor replacement typically runs in the $100 to $250 range including labor. Refrigerant leak repair or compressor replacement are more involved jobs and can range from $300 to $700 or more depending on parts, labor rates, and refrigerant type.

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