Kenmore Microwave F3 Error Code — What It Means
On most Kenmore microwave-oven combo platforms, F3 indicates a thermistor or temperature-sensing circuit fault. The official Kenmore fault chart defines F3 as “Thermistor short after cooking,” meaning the sensor does not register a temperature drop after the cooking cycle ends. This points to a failed thermal probe, damaged wiring, or a control board issue. A small number of Kenmore models built on certain GE platforms use F3 to indicate a keypad or membrane switch short instead. Because Kenmore is a private-label brand, the exact meaning depends on which manufacturer made your specific model. Check your full model number and the original OEM before ordering parts.
Common Causes
- Failed thermistor or thermal probe The temperature sensor itself has shorted or drifted out of spec and no longer reports accurate readings to the control board.
- Loose or corroded thermistor wiring The harness connector or wire leads between the sensor and the control board are damaged, corroded, or making intermittent contact.
- Defective control board The electronic controller has failed and misreads or cannot process the thermistor signal even when the sensor and wiring test good.
- Shorted membrane keypad (GE-platform models only) On models where F3 signals a keypad fault, a stuck button, moisture intrusion, or a damaged ribbon cable shorts the control panel circuit.
Step-by-Step Fix
- Disconnect power by unplugging the unit or switching off the dedicated breaker, then wait two minutes for internal capacitors to discharge.
- Identify your model’s actual manufacturer by looking up the full Kenmore model number to confirm whether your platform uses F3 for a thermistor fault or a keypad fault.
- Access the control area by removing the outer cabinet or grille panels according to your model’s service manual, exposing the thermistor leads and control board.
- Test the thermistor resistance by disconnecting its wire harness and measuring across the sensor terminals with a multimeter set to ohms. A good probe typically reads around 1.0 to 1.1 kΩ at room temperature.
- Inspect the wiring harness for burns, corrosion, or loose pins at both the thermistor connector and the control board socket, and repair or replace any damaged leads.
- Replace the thermistor if resistance is far out of range or if the sensor shows an open or dead short, then reassemble and test the microwave.
- Replace the control board if the thermistor and wiring both test correctly but the F3 code returns, since the controller can no longer interpret the sensor signal properly.
Parts Often Needed
| Part | Notes |
|---|---|
| Thermistor / Thermal Probe | Amazon | Match the part number on your existing sensor or use your Kenmore model number to cross-reference the correct probe for your platform. |
| Wiring Harness (Thermistor to Control Board) | Amazon | Order if the connector or leads show visible burn marks, corrosion, or broken wires that cannot be spliced safely. |
| Electronic Control Board / Controller Board | Amazon | Required when the thermistor and harness test good but F3 persists. Verify your exact model and OEM before purchasing. |
| Membrane Keypad / Control Panel Assembly | Amazon | Only for GE-platform Kenmore models where F3 indicates a keypad short. Inspect for stuck buttons or moisture damage before ordering. |
When to Call a Pro
Call a qualified appliance technician if you are uncomfortable working around high-voltage components, if you cannot safely access the control area or thermistor, or if the F3 code returns after you have replaced both the sensor and the wiring harness. Microwave ovens store dangerous voltage in their capacitors and magnetrons even when unplugged, so professional service is strongly recommended if you lack experience with microwave disassembly. A technician can also cross-reference your exact Kenmore model against OEM fault charts to confirm whether your F3 is thermistor-related or keypad-related and can supply the correct platform-specific parts.