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Error code reference

LG Refrigerator Error Code Water Tank Heater Error

Water Tank Heater open detected (separation of housing part, bad contact, wire disconnection).

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Water Tank Heater open detected (separation of housing part, bad contact, wire disconnection).

First step from the service manual

After separating MAIN PCB CN79 from PCB, measure resistance between Pink <-> White wire: shall be 72 ohm +/- 7%.

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

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What Water Tank Heater Error means on a LG refrigerator

The Water Tank Heater Error on an LG refrigerator indicates that the control system has detected an open circuit condition in the water tank heater circuit. This heater is responsible for preventing the water supply line or tank from freezing inside the refrigerator, which is a common requirement in models with internal water dispensing systems. An open circuit means the electrical path through the heater element or its wiring is broken, so the control board cannot confirm the heater is operational.

The fault is specifically triggered when the main PCB detects an interruption in continuity through the heater circuit. The primary diagnostic check involves disconnecting connector CN79 from the main PCB and measuring resistance across the Pink and White wires. A properly functioning water tank heater should read 72 ohms, plus or minus 7 percent (approximately 67 to 77 ohms). A reading significantly outside this range, or an open reading (infinite resistance), confirms the heater element or its wiring has failed.

The three most common physical causes are separation of the heater housing from its mounting, poor or corroded terminal contact at the connector, and a broken or disconnected wire somewhere along the harness. Because the connector is at CN79 on the main PCB, the fault can originate anywhere from the PCB terminal itself to the heater element at the water tank. Checking connector seating and wire integrity before condemning the heater element is essential for an accurate diagnosis.

Source: manufacturer service documentation.

Common causes of Water Tank Heater Error

  1. 01

    Loose or disconnected wiring harness

    Wiring / connection

    A wire in the harness running to the water tank heater may have worked loose or fully disconnected, breaking the circuit. Visually inspect the wiring from the CN79 connector at the main PCB all the way to the heater for any separation or visible damage.

  2. 02

    Poor or corroded connector contact at CN79

    Wiring / connection

    The connector at main PCB CN79 can develop poor contact due to corrosion, moisture intrusion, or terminal spread. Unplug and reseat the connector, then re-measure resistance between the Pink and White wires to see if contact is restored.

  3. 03

    Separated heater housing

    Part replacement

    The heater element housing can physically separate from its mount on the water tank, potentially straining or breaking the internal connection. Inspect the heater assembly for visible separation or cracking around the housing.

  4. 04

    Failed water tank heater element

    Part replacement

    The heater element itself may have burned out, producing an open circuit reading when tested. If the resistance measured between the Pink and White wires is far outside the 72 ohm plus or minus 7 percent specification, the heater element requires replacement.

  5. 05

    Damaged wire insulation or broken conductor

    Part replacement

    A wire in the circuit may have a broken internal conductor while the outer insulation appears intact, especially in areas subject to vibration or tight routing. A continuity check along each wire in the harness can isolate this type of failure.

See the test procedure for each cause

Frequently asked questions about Water Tank Heater Error

What does Water Tank Heater Error mean on a LG refrigerator?
This error means the main control board has detected an open circuit in the water tank heater circuit, which prevents it from confirming the heater is functional. The heater keeps the internal water tank from freezing. The fault is usually caused by a disconnected wire, a bad connector at CN79 on the main PCB, a separated heater housing, or a failed heater element. The proper resistance across the heater circuit should measure 72 ohms, plus or minus 7 percent.
How do I fix the Water Tank Heater Error on my LG refrigerator?
Start by disconnecting the CN79 connector from the main PCB and measuring resistance between the Pink and White wires using a multimeter. A reading of approximately 67 to 77 ohms indicates the heater element is intact, so the problem is likely a bad connection, corroded terminal, or broken wire in the harness. A reading of infinite resistance (open) means the heater element itself has failed and the component will need to be replaced. Always reseat the connector firmly before concluding the heater is bad.
Is the Water Tank Heater Error on an LG refrigerator a safety concern?
The error itself does not typically create an immediate safety hazard in most situations. However, a non-functional water tank heater can allow the internal water line or tank to freeze, which can block water dispensing or cause internal damage over time. It is best to address the fault promptly rather than leaving it unresolved, especially in refrigerators set to lower temperatures.
Will resetting my LG refrigerator clear the Water Tank Heater Error?
A power reset may temporarily clear the error display, but the code will return if the underlying electrical fault in the water tank heater circuit is not corrected. The control board continuously monitors the heater circuit, so any open condition will trigger the error again. A reset is not a fix and should only be used after completing the proper resistance check and resolving the wiring or component issue.
How much does it cost to repair the Water Tank Heater Error on an LG refrigerator?
Repair costs vary depending on the root cause. If the fix only requires reseating a connector or securing a loose wire, there may be no parts cost at all, though a service call fee typically ranges from 75 to 150 dollars. If the water tank heater element needs replacement, parts and labor combined generally range from 150 to 350 dollars depending on the specific model and local labor rates. Diagnosing whether the issue is a wiring problem or a failed component first can help avoid unnecessary parts expense.

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