Disconnect the convection oven’s power cord from its outlet. Pull the oven out so you can fit behind the appliance.
Locate and remove the top back panel, which sits against the control panel. This gives you access to the many wires and components hidden behind the control panel. The back panel is typically held in place by a series of screws on the side or top of the panel. Most panels lift up and away from the oven once loosened.
Disconnect the thermostat. The thermostat looks like a rectangular part connected in place behind the left-most burner knob. The thermostat will either pull out from its housing or loosen via the removal of one or two screws. Disconnect the wires that connect into the thermostat by pulling them away from the thermostat. Do not pull the wires themselves, but pull the plastic connector.
Open your KitchenAid convection oven’s front door and locate the thermostat thermal sensor bulb, which looks like a metal rod. The bulb is typically secured to the left, right or rear center of your oven by two brackets screwed in place, or the tube may be clipped in place. Unscrew or unclip the bulb to free it.
Feed the thermal bulb through the small hole in back of the oven. Once you cannot feed the bulb any farther, go to the back of the oven and pull the thermostat up, removing the remaining portion of the bulb from the oven.
Insert the thermal bulb into the oven cavity. Secure it to the brackets if applicable. Insert the plastic connector into the thermostat and then connect the thermostat back into its housing.