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A countertop microwave with its door closed, a plain glass measuring cup of water sitting still on the turntable behind the mesh window, the display showing plain digits.

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.

(844) 393-5858

Mon–Sat, 8am–8pm

  • Heating and magnetron
  • Microwave magnetron repair
  • Source: JennAir

Book a visit

Three short steps, about a minute.

or call (844) 393-5858

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 codeHeating 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 toMicrowave 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 asWhat 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.

MakeJennAir

JennAir microwaves looked at in place, with the breaker, the door switches and a one-minute heat test covered before any part is priced.

SourceJennAir 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. 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

Before you call

What a Microwave Error Code Is Telling You

All 7 causes, cheapest first

It also comes with

Close view of the control panel beside the side-hinged door with a mesh window of a built-in stainless microwave in a tall kitchen cabinet, a few abstract lit segments on its small display, the microwave cavity dark behind the closed mesh window. 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

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

More JennAir codes

LOCDOORPFDemoE03E11E21F3T3F4E1F4E4F6E0F7E9
All 21 JennAir codes

Heating and magnetron on other makes

Fisher & Paykel A5KitchenAid F3T4
All 4 codes of this kind
A stainless microwave hood combination mounted under white shaker wall cabinets in a US kitchen, the microwave's side-hinged door closed with its dark mesh window, a plain glass bowl visible faintly on the glass turntable inside the microwave, the lamp on its underside glowing softly onto a cooking surface that is cropped and out of focus at the bottom edge. 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.

 A stainless built-in microwave set flush into a tall walnut cabinet at eye level in a US kitchen, a thin steel trim frame around the microwave, its door closed with a dark mesh window and a plain glass dish on the glass tray inside the microwave, soft daylight from the side. 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.

 A stainless microwave drawer built into a light oak kitchen island under a marble counter in a US home, the microwave drawer slid fully open toward the camera to show its flat interior with a plain covered glass casserole dish inside, the control strip along the top edge of the microwave blank or showing plain digits only. 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 JennAir Product Help, over-the-range microwave: F3T4

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.

All service areas

Tampa BayFL · 31 areas

OrlandoFL · 30 areas

Miami / South FloridaFL · 47 areas

New York MetroNY · 75 areas

HoustonTX · 36 areas

ChicagoIL · 50 areas

Los AngelesCA · 95 areas

San DiegoCA · 31 areas

San Francisco Bay AreaCA · 74 areas

A family warming plates of food at a built-in microwave in a bright kitchen
For the heart of your home.

Questions
about F3T4.

Can I clear F3T4 myself?
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.

Back to your everyday

Still showing F3T4?

Three details make the booking useful: the characters or beeps just as they appeared, every character of the model number, and whether a cup of water still warms up. With those, the technician arrives already halfway to the answer.

Schedule a repair Call (844) 393-5858
(844) 393-5858 Schedule a repair