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Error code reference

Frigidaire Microwave Error Code F91

Door motor mechanism failure (F90 through F94).

Frigidaire codesFrigidaire microwave codes

Door motor mechanism failure (F90 through F94).

First step from the service manual

Turn off power for 10 seconds, then turn on power. Test the door latch again (try to start a Clean cycle). If it fails, check wiring of Lock Motor, Lock Switch and Door Switch circuits.

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

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What F91 means on a Frigidaire microwave

The F91 error code on a Frigidaire microwave indicates a door motor mechanism failure, grouped within the F90 through F94 fault range. This range covers failures in the motorized door latch system, which controls the physical locking and unlocking of the microwave door. The door motor mechanism is responsible for engaging and disengaging the lock when a cycle is initiated. When the control board does not receive confirmation that the lock motor has completed its travel or that the associated switches have changed state as expected, it registers an F91 fault and halts operation.

The system involved includes three closely related components: the lock motor itself, the lock switch, and the door switch. These work in sequence. The lock motor drives the latch mechanism, the lock switch confirms the latch position, and the door switch confirms the door is physically closed. A failure in any one of these components, or in the wiring connecting them to the control board, can trigger this code. Wiring faults such as broken connectors, corroded terminals, or pinched harness runs are common culprits alongside component failures.

Diagnosis begins with a power reset of at least 10 seconds to clear any transient control board faults. After restoring power, attempting to start a Clean cycle will test whether the door motor mechanism responds correctly. If the fault returns, the wiring of the lock motor circuit, lock switch circuit, and door switch circuit should be inspected for continuity, secure connections, and physical damage before replacing any individual component.

Source: manufacturer service documentation.

Common causes of F91

  1. 01

    Faulty lock motor

    Part replacement

    The lock motor that physically drives the door latch mechanism may have failed internally. If the motor does not run or does not complete its full travel when a cycle is started, the control board will register an F91 fault.

  2. 02

    Wiring harness fault

    Wiring / connection

    Broken wires, corroded terminals, or loose connectors in the lock motor, lock switch, or door switch circuits can interrupt the signals the control board expects. Inspect all connectors in these circuits for damage, corrosion, and secure seating.

  3. 03

    Defective lock switch

    Part replacement

    The lock switch confirms to the control board that the latch has moved into the locked position. A failed or misaligned lock switch will not send the expected signal even if the motor operates correctly, triggering the fault.

  4. 04

    Failed door switch

    Part replacement

    The door switch verifies that the microwave door is physically closed before the locking sequence can complete. A worn or broken door switch can cause the system to report a mechanism failure even when the motor and lock switch are functional.

  5. 05

    Control board fault

    Part replacement

    If all wiring and the lock motor, lock switch, and door switch test correctly, the main control board itself may have failed and is incorrectly registering or generating the F91 code.

See the test procedure for each cause

Frequently asked questions about F91

What does F91 mean on a Frigidaire microwave?
F91 indicates a door motor mechanism failure on a Frigidaire microwave. It falls within the F90 to F94 fault range, all of which relate to the motorized door latch system. The control board detected that the lock motor, lock switch, or door switch did not respond as expected during a door locking sequence. The microwave will not operate until the fault is resolved.
Will resetting the microwave clear the F91 error?
A power reset is the recommended first step and can clear the F91 code if the fault was caused by a temporary control board glitch. Turn off power to the microwave for at least 10 seconds, restore power, and then try starting a Clean cycle to test the door latch. If the error returns after the reset, there is a genuine hardware failure in the lock motor, lock switch, door switch, or associated wiring that requires further diagnosis.
Is it safe to use my Frigidaire microwave while the F91 code is showing?
No, you should not attempt to operate the microwave while the F91 fault is active. The door motor mechanism is part of the safety interlock system that ensures the door is properly latched before microwave energy is generated. A failure in this system means the microwave may not be safely secured, and operating it in this condition is a safety risk.
How do I fix the F91 error on my Frigidaire microwave?
Start by turning off power for 10 seconds and then restoring it, then attempt to start a Clean cycle to see if the door latch responds. If the fault returns, inspect the wiring and connectors on the lock motor, lock switch, and door switch circuits for damage or loose connections. If wiring appears intact, each component should be tested individually to identify which one has failed and needs replacement. Because this repair involves working near high-voltage components inside a microwave, many technicians recommend having a qualified repair professional perform the inspection.
How much does it cost to repair a Frigidaire microwave F91 error?
Repair costs vary depending on which component has failed. Replacing a lock switch or door switch is generally the least expensive fix, typically ranging from around $50 to $150 including parts and labor. A lock motor replacement may cost somewhat more, in the range of $80 to $200. If the control board is at fault, replacement costs can range from $150 to $350 or higher depending on the model and service rates in your area.

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