mypros+
Error code reference

Kenmore Oven Error Code F43

The microwave external cooling fan speed (as read by the tachometer input of the Appliance Control Board) is…

Kenmore codesKenmore oven codes

The microwave external cooling fan speed (as read by the tachometer input of the Appliance Control Board) is abnormally slow.

First step from the service manual

Check if the microwave external cooling fan is turning. If not turning or very slow, check 120VAC voltage at the fan.

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

MyPros+ Max

Get the full diagnostic procedure for F43.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What F43 means on a Kenmore oven

The F43 error code on a Kenmore oven indicates that the Appliance Control Board has detected an abnormally low rotation speed from the microwave external cooling fan. This fan is responsible for dissipating heat generated by the microwave magnetron and other high-voltage components during operation. The control board monitors fan speed through a tachometer input, which reads pulses generated by a Hall effect sensor or similar feedback mechanism built into the fan motor. When the pulse frequency falls below the expected threshold, the board registers F43 to alert the user and technician that cooling performance is compromised.

The most direct cause of this fault is a fan motor that has failed mechanically or electrically. A fan that is not spinning at all, or spinning too slowly, cannot adequately protect the microwave components from heat damage. The first step is to observe whether the fan is physically turning. If it is not moving or is sluggish, the next check is to confirm that 120VAC is being supplied to the fan motor terminals. Absence of voltage points to a control or wiring issue, while correct voltage with poor fan performance points to a failing motor.

Beyond the fan motor itself, contributing causes can include a blocked or obstructed fan blade, a wiring harness problem introducing resistance into the circuit, or a faulty tachometer feedback signal. The control board may also be misreading a valid signal if the tachometer circuit or the board itself is defective. Identifying whether the fault is in the motor, the power supply to the motor, or the feedback signal path is the key to an accurate repair.

Source: manufacturer service documentation.

Common causes of F43

  1. 01

    Failed Fan Motor

    Part replacement

    The external cooling fan motor has worn bearings or a burned winding and can no longer spin at the correct speed. Check if the fan blade is turning during microwave operation and listen for unusual noise or humming without rotation.

  2. 02

    No 120VAC Power to the Fan

    Wiring / connection

    A break in the wiring harness, a failed relay on the control board, or a blown fuse can cut power to the fan motor entirely. Measure voltage at the fan motor terminals with a multimeter during operation to confirm supply voltage.

  3. 03

    Obstructed or Jammed Fan Blade

    Wiring / connection

    Debris, grease buildup, or a dislodged component can physically block the fan blade from spinning freely. Inspect the fan assembly for obstructions and attempt to rotate the blade by hand with power disconnected.

  4. 04

    Faulty Tachometer Feedback Circuit

    Part replacement

    If the fan motor is spinning at normal speed but the tachometer signal returning to the control board is weak or absent, the board will still register F43. Inspect the tachometer wiring connections and sensor for damage or corrosion.

  5. 05

    Defective Appliance Control Board

    Part replacement

    If the fan motor, power supply, and tachometer circuit all test correctly, the control board itself may be misinterpreting the speed signal. A board with a damaged tachometer input circuit will need to be replaced.

See the test procedure for each cause

Frequently asked questions about F43

What does F43 mean on a Kenmore oven?
The F43 code means the Appliance Control Board has detected that the microwave external cooling fan is spinning at an abnormally slow speed, or has stopped spinning entirely. The board monitors fan speed through a tachometer input and triggers this fault when the rotation rate falls below an acceptable level. This is a protective alert designed to prevent heat damage to microwave components. The oven should not be used until the fan issue is resolved.
Can I fix the F43 error on my Kenmore oven myself?
Some causes of F43 are accessible to a knowledgeable DIYer. You can safely inspect the fan for physical obstructions and check for obvious wiring damage with the appliance unplugged. However, testing for 120VAC at the fan motor and diagnosing the tachometer circuit requires working near high-voltage components, which carries serious safety risks. Motor and control board replacement are best handled by a qualified technician if you are not experienced with appliance electrical repair.
Is it safe to keep using my oven when the F43 code is showing?
It is not recommended to continue using the microwave function while F43 is active. The cooling fan protects the magnetron and other internal components from overheating, and operating without adequate airflow can cause permanent damage. The oven bake and broil functions may still work, but the microwave portion should remain off until the fan problem is corrected.
Will resetting the oven clear the F43 error code?
Disconnecting power to the oven briefly may temporarily clear the F43 code, but the fault will return as soon as the control board detects the slow fan speed again during operation. A reset does not fix the underlying problem with the fan motor, wiring, or tachometer circuit. The code will continue to appear until the root cause is repaired.
How much does it cost to repair a Kenmore oven F43 error?
Repair costs vary depending on what component has failed. A replacement cooling fan motor typically ranges from $30 to $80 in parts. If the Appliance Control Board needs replacement, parts alone can range from $100 to $250 or more. Adding professional labor, total repair costs generally fall between $150 and $400 depending on the specific failure and your location.

Related Kenmore oven codes

All Kenmore oven codes
View all 33 Kenmore oven codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass