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Error code reference

KitchenAid Microwave Error Code F6

MW relay failure (relay 4903 contact may have welded closed).

KitchenAid codesKitchenAid microwave codes

MW relay failure (relay 4903 contact may have welded closed).

First step from the service manual

Unplug microwave oven or disconnect power, then check wiring to Relay 4903 and check if relay contact has welded closed.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What F6 means on a KitchenAid microwave

The F6 error code on a KitchenAid microwave indicates a microwave relay failure, specifically involving Relay 4903. This relay is a high-voltage switching component that controls power delivery to the magnetron or other critical microwave circuits. When the control board detects that Relay 4903 is not responding correctly, or that its contact has failed in a closed position (known as a welded contact), it triggers the F6 fault to prevent further operation. A welded contact occurs when the relay's internal switching contacts fuse together due to excessive current or arcing, causing the circuit to remain permanently closed even when the relay should be open.

A welded relay contact is a serious condition because it means the microwave may be unable to shut off power to the high-voltage circuit on command. This creates both a functional failure and a potential safety hazard. The relay contact can weld closed due to repeated high-current switching cycles, a faulty magnetron drawing excessive current, or general component aging. Wiring issues between the control board and the relay, such as loose connectors, corroded terminals, or damaged wire insulation, can also cause the relay to behave erratically and trigger this fault code.

The primary diagnostic approach requires disconnecting power to the microwave completely before inspecting Relay 4903 and its associated wiring harness. A technician should check all wiring connections to the relay for damage or corrosion, then physically test the relay contact to determine whether it has welded closed. If the contact is confirmed welded, the relay must be replaced before the microwave can safely return to service.

Source: manufacturer service documentation.

Common causes of F6

  1. 01

    Welded Relay 4903 Contact

    Part replacement

    The relay's internal switching contacts have fused together due to arcing or excessive current, leaving the circuit permanently closed. This is confirmed by physically testing the relay contact after disconnecting power.

  2. 02

    Faulty or Failed Relay 4903

    Part replacement

    The relay itself may have failed electrically without a visible welded contact, causing the control board to detect an abnormal switching response. Replacing the relay resolves this condition.

  3. 03

    Wiring Harness Damage or Loose Connections

    Wiring / connection

    Damaged wire insulation, loose connectors, or corroded terminals in the wiring leading to Relay 4903 can cause incorrect signals and trigger the F6 fault. Inspect all connectors and wiring to the relay for continuity and secure seating.

  4. 04

    Excessive Current Draw from the Magnetron

    Part replacement

    A failing magnetron that draws higher than normal current can repeatedly stress the relay contacts during switching cycles, eventually causing them to weld. If the relay has failed more than once, the magnetron should be evaluated as a contributing cause.

  5. 05

    Control Board Fault

    Part replacement

    In some cases, the control board may be sending incorrect signals to Relay 4903 or misreading its feedback, generating a false F6 error. This is typically diagnosed after the relay and wiring have been ruled out.

See the test procedure for each cause

Frequently asked questions about F6

What does F6 mean on a KitchenAid microwave?
The F6 code indicates a microwave relay failure involving Relay 4903. The fault is triggered when the control board detects that this relay is not switching correctly, or that its contact has welded closed in the on position. A welded contact means the circuit cannot be opened on command, which is both a functional failure and a safety concern. Power must be disconnected before any inspection or repair is attempted.
Can I fix the F6 error on my KitchenAid microwave myself?
Diagnosing and repairing F6 involves working near high-voltage components, so this repair is best handled by a qualified appliance technician. The first step is always to unplug the microwave and allow the high-voltage capacitor to discharge before touching any internal components. A technician will inspect the wiring to Relay 4903, test the relay contact, and replace the relay if it has failed or welded closed. Attempting this repair without proper training and tools carries a serious risk of electric shock.
Is it safe to use my KitchenAid microwave when it shows F6?
No, the microwave should not be used while displaying F6. A welded relay contact means the microwave may be unable to shut off its high-voltage circuit as intended, which poses a safety risk. Discontinue use and unplug the appliance until the relay has been inspected and the fault resolved.
Will resetting my KitchenAid microwave clear the F6 error?
Unplugging the microwave and restoring power may temporarily clear the F6 code, but if Relay 4903 has physically failed or its contact has welded closed, the fault will return. The underlying hardware problem must be identified and corrected for the error to be resolved permanently. Do not rely on a reset as a fix for this fault.
How much does it cost to repair an F6 error on a KitchenAid microwave?
Repair costs vary depending on whether the issue is limited to the relay or involves additional components like the wiring harness or control board. Relay replacement parts typically range from $15 to $60, while labor costs for a qualified technician can add $80 to $150 or more depending on your location. If the magnetron is also found to be contributing to the relay failure, total repair costs can increase significantly. Getting a diagnostic estimate before committing to repairs is recommended.

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