--- title: "JennAir F3T4: the sensor that guards the magnetron from heat" description: "What F3T4 means on JennAir F3T4: the sensor that guards the magnetron from heats, what to check before booking, and when it is not a failure at all." url: "https://microwaverepair.center/error-codes/jennair-f3t4/" --- # JennAir F3T4: the sensor that guards the magnetron from heat The magnetron in a JennAir hood combination runs hot, so a thermistor watches it and the control cuts power before damage. ## What F3T4 actually means. The magnetron in a JennAir hood combination runs hot, so a thermistor watches it and the control cuts power before damage. When that thermistor or its wiring reads out of range, F3T4 appears and the control stops heating rather than run the tube without protection. JennAir microwave display · also shown as F3 T4 What to do when F3T4 shows on the microwave ### Kind of code Heating and magnetron The microwave ran a cycle and the control saw no heat come of it, or saw the power section behave strangely. The cause sits somewhere in the chain that makes the energy: the magnetron, the high-voltage diode and capacitor, the transformer that feeds them. All of it lives behind the outer cabinet, where a capacitor keeps a dangerous charge even unplugged, so after a restart the owner's part ends at booking the visit. ### Usually leads to Microwave magnetron repair Replacing the tube that makes a microwave's heat, after proving the parts that feed it are sound, and renewing the waveguide cover and any pitted metal where sparks have been. ### Shows up as What a Microwave Error Code Is Telling You A microwave error code may be a letter and a number on the display, a lock or demo word, a row of dashes, or a beep with a blinking clock, and it can show while the microwave still heats or block every key until it is cleared. ### Make JennAir JennAir microwaves looked at in place, with the breaker, the door switches and a one-minute heat test covered before any part is priced. ### Source JennAir Product Help, over-the-range microwave: F3T4 From JennAir's help pages for its microwave hood combinations (Euro-style, including the convection models). The code set varies with the control generation, so a code missing from your model's manual may not apply to it. ## Before you book, in this order. Each step comes from JennAir's own guidance for F3T4 on its microwaves. Follow it to the end: the last card says whether this is a visit. 01 Turn the microwave off at the circuit breaker, count a full minute, then restore power. 02 Give it a minute on standby; a code that does not reappear was likely a one-time glitch, so run a short cycle to confirm. 03 Clear anything stored on top of the unit and check that the grille is not blocked, since cooling air must flow through it. 04 If F3T4 returns, stop using the microwave and book a visit; the parts sit beside the high-voltage section. ### Still there? It usually turns into [microwave magnetron repair](https://microwaverepair.center/services/microwave-magnetron-repair/). Book with the code and the model number. ### What not to do F3T4 is a sensor reading, so a new magnetron is rarely the first answer. Cycling the door will not clear it, because it is not a door code. ## What you may notice with it. The microwave problems F3T4 tends to arrive with. Answer these at the microwave before anyone is booked. [All problems](https://microwaverepair.center/problems/) Before you call ### [What a Microwave Error Code Is Telling You](https://microwaverepair.center/problems/microwave-error-code/) [All 7 causes, cheapest first](https://microwaverepair.center/problems/microwave-error-code/) It also comes with - [**Microwave Runs but Food Stays Cold**](https://microwaverepair.center/problems/microwave-not-heating/) - [**Microwave Shuts Off Before the Timer Ends**](https://microwaverepair.center/problems/microwave-stops-mid-cycle/) Problem ### What a Microwave Error Code Is Telling You 7 causes, cheapest first Where F3T4 usually leads ## Microwave magnetron repair. **Magnetron and waveguide cover · moderate to highest.** Book a visit [What the job involves](https://microwaverepair.center/services/microwave-magnetron-repair/) ## JennAir microwaves. JennAir microwaves looked at in place, with the breaker, the door switches and a one-minute heat test covered before any part is priced. [JennAir microwave repair](https://microwaverepair.center/brands/jennair/) More JennAir codes [LOC](https://microwaverepair.center/error-codes/jennair-loc/) [DOOR](https://microwaverepair.center/error-codes/jennair-door/) [PF](https://microwaverepair.center/error-codes/jennair-pf/) [Demo](https://microwaverepair.center/error-codes/jennair-demo/) [E03](https://microwaverepair.center/error-codes/jennair-e03/) [E11](https://microwaverepair.center/error-codes/jennair-e11/) [E21](https://microwaverepair.center/error-codes/jennair-e21/) [F3T3](https://microwaverepair.center/error-codes/jennair-f3t3/) [F4E1](https://microwaverepair.center/error-codes/jennair-f4e1/) [F4E4](https://microwaverepair.center/error-codes/jennair-f4e4/) [F6E0](https://microwaverepair.center/error-codes/jennair-f6e0/) [F7E9](https://microwaverepair.center/error-codes/jennair-f7e9/) [All 21 JennAir codes](https://microwaverepair.center/error-codes/#codes-jennair) Heating and magnetron on other makes [Fisher & Paykel A5](https://microwaverepair.center/error-codes/fisher-and-paykel-a5/) [KitchenAid F3T4](https://microwaverepair.center/error-codes/kitchenaid-f3t4/) [All 4 codes of this kind](https://microwaverepair.center/error-codes/#family-heating) JennAir builds this ### Microwave hood combination The microwave that hangs from the wall cabinets above the burners, heating food in its cavity while its own fan, light and filters handle the steam and grease rising from the pans beneath it. JennAir builds this ### Built-in microwave A microwave set into a tall cabinet or a wall of cabinetry at eye level, either a countertop body wrapped in a trim kit or a true built-in model, including speed and convection microwaves that brown as well as heat. JennAir builds this ### Microwave drawer A microwave built under a counter or into a kitchen island that opens like a drawer at the touch of a key, with a motor and gears sliding its cavity out toward you. ## In JennAir's own words > There may be a problem with the Magnetron Temperature Thermistor or the associated wiring. [JennAir Product Help, over-the-range microwave: F3T4](https://producthelp.jennair.com/Cooking/Microwaves/Over-the-Range_Microwave/Error_Code/Starts_with_F/Starts_with_F3/F3T4_-_Error_Code_-_Over-the-Range_Microwave) [JennAir Product Help, over-the-range microwave: F3T4](https://producthelp.jennair.com/Cooking/Microwaves/Over-the-Range_Microwave/Error_Code/Starts_with_F/Starts_with_F3/F3T4_-_Error_Code_-_Over-the-Range_Microwave) Every code on this site is taken from the manufacturer's documentation, never from a forum or a parts listing. From JennAir's help pages for its microwave hood combinations (Euro-style, including the convection models). The code set varies with the control generation, so a code missing from your model's manual may not apply to it. ## JennAir F3T4 microwave repair, where we come out. The same visit in every metro below: the code, the model number, and a diagnosis before any part is ordered. 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Turn the microwave off at the circuit breaker, count a full minute, then restore power. If it comes back, it needs a visit. ### Is my JennAir magnetron finished if it shows F3T4? Not by the code alone. JennAir names the magnetron's temperature thermistor and its wiring, which are far more common repairs than the tube. ### Why did my JennAir stop mid-reheat with F3T4? The protection sensor gave an impossible reading, and the control shut heating off to protect the magnetron. ### Can a JennAir owner replace the magnetron sensor? No. It is inside the case next to a capacitor that holds a charge after unplugging, so a technician does it. --- **[Read on the site: JennAir F3T4: the sensor that guards the magnetron from heat](https://microwaverepair.center/error-codes/jennair-f3t4/)** **[Book a visit with MicrowaveRepair.center](https://microwaverepair.center/schedule/)**