Maytag Range Error Code 4d21

Code 4d21 means the oven's control board detected no rotation or very low RPM from the reverse airflow fan motor in the upper or single oven cavity. The board monitors the fan's speed signal during operation, and when that signal is absent or too weak, it stores this fault. The root cause is typically a failed fan motor, a wiring problem, or a physically blocked fan blade.

Your range may still heat in standard bake mode if only the convection fan circuit is affected, but convection cooking will not function correctly without proper airflow. Using the oven with this fault active means food will not cook evenly during convection cycles. Running the oven in this condition for extended periods is not recommended, as a seized or struggling fan motor can generate excess heat around the motor assembly.

Clearing the code by resetting power will erase the fault display temporarily, but 4d21 will return as soon as the oven attempts to run the reverse airflow fan and still detects no RPM signal. A reset does not repair the underlying mechanical or electrical fault. The fan motor, its wiring, and the fan blade all need to be physically inspected and tested before the repair can be considered complete.

Start by disconnecting power to the range and locating the reverse airflow fan motor in the upper oven cavity. Visually inspect the fan blade for obstructions and check that all wiring connectors to the motor are seated firmly and show no burn marks or broken wires. If the wiring looks intact, use a multimeter to test the motor windings for continuity. A motor with an open winding needs to be replaced. If the motor and wiring both test good, the control board may be the fault source.

If the fix is a blocked fan blade that only needs clearing, the repair costs nothing beyond your time. A replacement reverse airflow fan motor typically costs between $40 and $120 for the part depending on the model, plus labor if you hire a technician. A professional service call for this repair generally runs $150 to $300 total. If the control board is the cause, board replacement can push costs to $200 to $400 or more in parts and labor.