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Error code reference

LG Microwave Error Code E-Ct

Cooling fan motor PCB temperature sensor short circuit error.

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Cooling fan motor PCB temperature sensor short circuit error.

First step from the service manual

Repair the short circuit.

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

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What E-Ct means on a LG microwave

The E-Ct error code on an LG microwave indicates a short circuit condition in the PCB temperature sensor that monitors the cooling fan motor. This sensor is a thermistor or similar thermal sensing component mounted on or near the control board, designed to detect overheating in the cooling fan motor circuit. When the sensor's resistance drops to near zero due to a short circuit, the control board interprets this as an abnormal reading and triggers the E-Ct fault to prevent damage to the electronics.

A short circuit in this sensor circuit can occur in the wiring harness connecting the sensor to the PCB, within the sensor component itself, or at the PCB connection points. Damaged insulation, pinched wires, moisture intrusion, or a failed sensor component are the most common physical causes. Because the sensor is part of the thermal protection system for the fan motor, the microwave will typically halt operation until the fault is resolved.

The first step in diagnosis is locating and repairing the short circuit. This involves inspecting the sensor wiring from the connector on the PCB through to the sensor body, checking for any points where two conductors may be contacting each other or where a conductor is grounding against the chassis. If the wiring is intact, the sensor component itself should be tested for a shorted condition and replaced if it fails to show proper resistance values.

Source: manufacturer service documentation.

Common causes of E-Ct

  1. 01

    Shorted temperature sensor component

    Part replacement

    The thermistor or temperature sensor on the PCB can fail internally, causing its resistance to drop to near zero and produce a short circuit reading. Test the sensor directly with a multimeter to confirm a shorted condition.

  2. 02

    Damaged sensor wiring harness

    Wiring / connection

    The wiring between the sensor and the control board can become pinched, frayed, or have compromised insulation, causing two conductors to contact each other. Visually inspect the full length of the harness for damage or pinch points.

  3. 03

    Moisture or contamination on PCB

    Wiring / connection

    Grease, steam, or condensation inside the microwave cavity can reach the control board and create a conductive path across the sensor circuit terminals. Inspect the PCB for visible moisture, corrosion, or residue around the sensor connector.

  4. 04

    Loose or corroded connector at PCB

    Wiring / connection

    A corroded or improperly seated sensor connector at the PCB can cause abnormal resistance readings that the board interprets as a short. Remove and reseat the connector, inspecting the terminals for corrosion or deformation.

  5. 05

    Failed control board

    Part replacement

    If the sensor and wiring both test correctly but the error persists, the PCB itself may have a fault in the sensor monitoring circuit. Board replacement would be required in this scenario.

See the test procedure for each cause

Frequently asked questions about E-Ct

What does E-Ct mean on a LG microwave?
The E-Ct code on an LG microwave indicates a short circuit error in the PCB temperature sensor that monitors the cooling fan motor. The control board has detected that the sensor circuit resistance has dropped abnormally, which signals a short circuit condition. The microwave stops operating to protect its internal components until the fault is diagnosed and repaired.
Can I fix the E-Ct error myself?
Some causes, such as a loose connector or minor wiring damage, can potentially be addressed by a skilled DIYer who is comfortable working inside appliances and following proper safety precautions. However, microwave capacitors can retain a lethal electrical charge even when unplugged, so the internal components should only be accessed by someone who knows how to safely discharge the capacitor. If the control board or sensor component needs replacement, a qualified technician is recommended.
Is it safe to use my LG microwave while it shows E-Ct?
No, you should not attempt to use the microwave while the E-Ct error is active. The error indicates a fault in the thermal protection circuit for the cooling fan motor, which means the appliance cannot properly monitor for overheating. Continued use without resolving the fault could risk further damage to the control board or other internal components.
Will resetting my LG microwave clear the E-Ct error?
A simple reset, such as unplugging the microwave and plugging it back in, is unlikely to permanently clear the E-Ct error because it is caused by a physical short circuit in the sensor or its wiring. The fault will return as soon as the microwave re-checks the sensor circuit. The underlying short circuit must be located and repaired before the error will clear.
How much does it cost to repair an E-Ct error on an LG microwave?
Repair costs vary depending on what component has failed. If only a wiring repair is needed, technician labor costs might range from roughly 75 to 150 dollars. If the temperature sensor itself requires replacement, parts and labor combined could run from around 100 to 200 dollars. A control board replacement is the most expensive scenario, potentially ranging from 150 to 350 dollars or more depending on the model and labor rates in your area.

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