Ventilation motor stays on high, will not go to med or low setting
Answer John, The relay on the smart board WB27X10604 could be the issue, but you may want to start at the control panel WB07X10633 first.
You may have a "stuck" key pad, making the high speed a continuous circuit, and the Med or Low speed settings inoperable. If you remove power to the microwave, lower the control panel and disconnect the key pad ribbon from the smart board, then reapply power. If the vent motor still runs at the high speed, replace the smart board. If the vent motor doesn't run, replace the control panel.
How do I take the front panel cover off the keyboard of my GE microwave to replace the control board?
To remove the keypad on your microwave, you will remove 3 screws at the front top edge of the cabinet that hold the air grill on. Disconnect power and remove the grill. Once the air grill is removed there is a screw that hold the control panel in place. Remove the screw and lift up and out to remove the control panel.