JennAir JMV Code F3T4: magnetron temperature thermistor

What F3T4 means

On JennAir over-the-range microwave hoods such as the JMV9196CS or JMV8000 series, F3T4 indicates a possible problem with the magnetron temperature thermistor or its wiring. That sensor keeps an eye on the heat of the magnetron, the part that makes microwave energy. When its signal is lost, the control stops cooking to protect the magnetron and shows F3T4. The unit may run again after resting, then stop with the same code.

Common causes of F3T4

Magnetron temperature thermistor has failed
Wire or connector to the thermistor is loose
Magnetron is actually overheating and the sensor is reporting it

✓ One safe check you can try

1. Press Stop/Cancel and let the microwave rest for at least thirty minutes. 2. Keep the vent openings free of grease and clutter. 3. Do not run it empty. 4. Try a short test with a cup of water. 5. If F3T4 returns, stop using the microwave and call us.

! Why to stop there

A real magnetron overheat and a bad sensor look the same on the display.
The magnetron runs at high voltage, so only a trained technician should be near it.
Running a microwave that is overheating can ruin an expensive part.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

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Other Microwave codes

F8 E4JennAir Built-In Microwave Code F8 E4: exhaust air sensor SEJennAir JMV Code SE: keypad problem F8E5JennAir JMV Code F8E5: exhaust air temperature sensor F9JennAir JMV Code F9: appliance or relay control board F9Q1JennAir JMV Code F9Q1: touch pad problem FC E1JennAir OTR Microwave Code FC E1: router connection timed out FC E2JennAir OTR Microwave Code FC E2: appliance cannot reach the router FC E3JennAir OTR Microwave Code FC E3: link to the router was lost

F3T4F3T4 questions

Why is F3T4 marked as higher priority?

Because the thermistor protects the magnetron. If the magnetron is truly hot, more use can destroy it. Giving the unit a rest and getting it tested is cheaper than replacing the tube.

Can poor airflow cause F3T4?

Yes, blocked vents or a cabinet fit that traps heat may raise temperatures. Clear the openings, but if the code returns after cooling, the sensor or the magnetron needs a proper test.

Will the microwave work after cooling down?

Maybe for a few minutes, then F3T4 may come back. That pattern points to a real heat problem or a weak sensor, and either needs to be checked.