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Error code reference

Daewoo Microwave Error Code Err 3

Thermistor circuit fault

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Thermistor circuit fault — thermistor reads open or shorted, or heater circuit failure detected.

First step from the service manual

Check continuity of thermistor (resistance should be approx 200k–300kΩ at room temperature); if 0Ω or infinite, replace thermistor.

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

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What Err 3 means on a Daewoo microwave

Err 3 on a Daewoo microwave indicates a fault in the thermistor circuit. The thermistor is a temperature-sensitive resistor that monitors the internal cavity or component temperature during operation. At room temperature, a healthy thermistor should read approximately 200k to 300k ohms of resistance. When the control board detects a reading outside this expected range, either 0 ohms (a short circuit) or infinite resistance (an open circuit), it triggers Err 3 and halts operation to prevent damage or unsafe conditions.

The two primary fault conditions are a shorted thermistor and an open thermistor. A short occurs when the thermistor's resistance drops to or near zero, which can happen due to physical damage, moisture intrusion, or overheating of the component itself. An open circuit occurs when the thermistor or its wiring loses continuity entirely, often caused by a broken wire, a failed solder joint, or a thermistor that has burned out. Either condition causes the control board to lose its temperature reference signal, making safe operation impossible.

Err 3 can also indicate a heater circuit failure in models with a convection or grill heater function. In these cases, the fault may not be in the thermistor itself but in the wiring harness connecting it to the control board, a corroded connector, or a board-side input failure. Diagnosis should begin with a continuity and resistance check of the thermistor using a multimeter, followed by inspection of the harness and connector pins for damage or corrosion before replacing any components.

Source: manufacturer service documentation.

Common causes of Err 3

  1. 01

    Failed thermistor (open circuit)

    Part replacement

    The thermistor has burned out or broken internally, causing infinite resistance on a multimeter. This is the most common cause and is confirmed by checking resistance across the thermistor terminals, which should read 200k to 300k ohms at room temperature.

  2. 02

    Shorted thermistor

    Part replacement

    Physical damage, overheating, or moisture intrusion can cause the thermistor to short, dropping its resistance to near 0 ohms. A multimeter reading at or close to 0 ohms across the thermistor terminals confirms this fault.

  3. 03

    Damaged or disconnected wiring harness

    Wiring / connection

    The wires connecting the thermistor to the control board can break, corrode, or pull loose from their connector. Inspect the harness visually and check continuity along each wire before replacing the thermistor itself.

  4. 04

    Corroded or loose connector pins

    Wiring / connection

    The connector at the control board or thermistor end can develop corrosion or lose contact, mimicking an open thermistor circuit. Reseating or cleaning the connector pins may resolve the error without parts replacement.

  5. 05

    Heater circuit failure

    Part replacement

    On models with convection or grill heater functions, a fault in the heater circuit can also trigger Err 3. If the thermistor checks out within spec, inspect the heater circuit components and wiring for continuity faults.

See the test procedure for each cause

Frequently asked questions about Err 3

What does Err 3 mean on a Daewoo microwave?
Err 3 means the control board has detected a fault in the thermistor circuit. The thermistor is a temperature-sensing component that should read approximately 200k to 300k ohms at room temperature. If it reads 0 ohms or infinite resistance, the board cannot monitor internal temperature and shuts the unit down. A wiring harness fault or heater circuit failure can also trigger this code.
Can I fix Err 3 on my Daewoo microwave myself?
A knowledgeable DIYer can diagnose this error using a multimeter to check the thermistor resistance. If the reading is 0 ohms or infinite at room temperature, the thermistor needs to be replaced. Wiring and connector issues can also be addressed without professional help, but any work inside a microwave should be done with the unit unplugged and after discharging the high-voltage capacitor, which can hold a lethal charge even when the power is off.
Is it safe to use my Daewoo microwave while Err 3 is showing?
No. The microwave has disabled itself because it cannot monitor internal temperature, which is a safety function. Operating the unit without a working thermistor circuit could allow components to overheat without detection. Do not attempt to bypass the error or force the unit to run until the fault is diagnosed and repaired.
Will resetting my Daewoo microwave clear the Err 3 code?
A power reset by unplugging the unit for a few minutes may temporarily clear the display, but the error will return as soon as the control board re-checks the thermistor circuit. Err 3 indicates a hardware fault, so a reset alone will not fix the underlying problem. The thermistor, wiring, or heater circuit must be inspected and repaired to resolve the code permanently.
How much does it cost to repair Err 3 on a Daewoo microwave?
If the thermistor itself is the problem, parts are generally inexpensive, typically in the range of a few dollars to around twenty dollars depending on the model. If a professional technician is needed for diagnosis and replacement, labor costs typically bring the total repair into the range of fifty to one hundred fifty dollars. More complex faults involving the heater circuit or control board can increase that cost significantly, and it may be worth comparing repair cost to the price of a replacement unit.

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