Maytag Microwave Error Code Err4

Err4 means the microwave's control board has detected a failure in the high voltage (H.V.) board. The H.V. board converts household current into the high-voltage power required to run the magnetron and heat food. When this board fails or loses communication, the microwave shuts down cooking functions and displays Err4.

No. Err4 indicates the high voltage board has failed, and the microwave will not heat food in this state. Attempting to force the unit to run with a known H.V. board fault is not safe and can cause further damage to other components. Stop using the microwave until the H.V. board is inspected and replaced.

Unplugging the microwave and plugging it back in may temporarily clear the error display, but Err4 will return as soon as the control board checks the H.V. board again and confirms the fault. A power cycle does not fix a failed H.V. board. The error will persist until the board is replaced or the underlying fault is corrected.

The primary fix for Err4 is replacing the high voltage board. Before ordering a part, unplug the microwave and check that all wiring harness connectors to the H.V. board are fully seated and undamaged. If connections are secure and the board shows visible burn marks or damage, replace the H.V. board. Because the high-voltage capacitor inside a microwave can hold a lethal charge even after unplugging, discharging the capacitor before any internal work is mandatory. If you are not experienced with high-voltage electronics, a qualified appliance technician should handle this repair.

A replacement Maytag high voltage board typically costs between $50 and $150 depending on the specific model. If you hire a technician, expect to add $75 to $150 or more in labor, bringing the total repair cost to roughly $125 to $300. For older or lower-cost microwaves, compare the repair cost against replacement before committing, since the H.V. board is one of the more expensive internal components.