The short answer
F4 E8 on this Maytag appliance is a microwave inverter fault: the table names the inverter and its wiring. The inverter is the high-voltage supply that drives the magnetron, and it is not an owner-serviceable part under any circumstances. Stop using the microwave function and leave the diagnosis to a technician.
Code table
Reference| code | meaning | owner-checkable |
|---|---|---|
| F4 E8 | There may be a problem with the Microwave Inverter, or the associated wiring. | no |
| F4 E7 | Do not use the Oven Meat Probe in the Microwave, they have different resistance values. | see page |
| F4E1 | There may be a problem with the Cavity Temperature Thermistor or the associated wiring. | see page |
What you observe
- The microwave runs but nothing heats — The turntable and light behave while no power reaches the food.
- A buzz or hum that was not there before — A change in the running note of the high-voltage stage.
- NEAR MISS — the lower oven still cooks normally — On a combination appliance the oven cavity is a separate system with its own codes.
Likeliest causes first
- The inverter itself — First, because the code names it: it is a high-stress component that switches large currents, and it fails outright rather than gradually.
- The wiring or connector to the inverter — Second: the high-voltage loom is short, tight and heat-cycled, and a poor connection reproduces the fault exactly.
- The magnetron loading the inverter — Last: a failing magnetron can drag the supply out of range so the inverter reports first, which is why both are tested together.
Check in this order
- Stop using the microwave and note the code — There is no owner test on a high-voltage circuit; the useful step is to stop and record.
- Cut the breaker for a minute and try once more — This distinguishes a latched state from a hard failure, and it is the last free step.
- Leave everything else to a technician — The capacitor in this circuit holds a dangerous charge with the appliance unplugged.
Owner-safe steps
- Record the code and stop using the microwave — A microwave that cannot heat is doing no cooking anyway, and running it stresses the failing stage.
About 5 min
- Cut the breaker for a minute, then test with a cup of water — If it heats, the fault was latched; if the code returns, it is hardware.
About 10 min
- STOP HERE — everything past this is behind the cover — The high-voltage capacitor must be discharged by someone equipped to do it.
Safety first
Safety
Unplug the appliance or switch off its breaker before removing any panel — a capacitor can hold a charge after the power is off. An oven carries a heavy element circuit behind the rear panel, and the cavity stays dangerous long after the heat is off. Leave the door lock and its switch wired exactly as they are.
When to call
Call as soon as the code survives a power cycle, and do not open the appliance in the meantime. The high-voltage section of a microwave holds a charge after it is unplugged, which is why this is one of the few appliance repairs with no owner-side step at all. Expect the technician to test the inverter and the magnetron together, because each can make the other look faulty.
Neighbouring codes — F4 E7 and F4E1 appear beside F4 E8 in the table and are recorded against different hardware — different questions with different answers. A shared prefix on this brand is not a shared fault.
What this page does not cover
This page is written for the Maytag oven class rather than for one model line, and F4 E8 is read exactly as the shared table records it. If your family or model has its own page, that page is the more specific answer and it is linked below — go there first when your model is named. Left out deliberately: connector positions, wiring colours and part numbers, which are family-specific.
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Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
