Thermador gas cooktops use an igniter system, commonly known as a glow plug, to light the surface burners. The igniter heats rapidly to a temperature setting that causes the gas valve to open and lights the cooktop burner. Igniters are fragile and typically wear out before any other part on the cooktop. Replacing the igniter takes less than an hour to do with common household tools. Use work gloves to protect your hands from the sharp metal below the Thermador cooktop.
Close the valve in the gas line connected to the Thermador oven. Unplug the cooktop's electrical cord from the wall outlet.
Remove the screws under the front edge of the Thermador cooktop below the cabinet to release the cooktop from the countertop.
Put on work gloves then raise the cooktop at an angle. Recruit a friend to hold up the appliance while you work on the igniter underneath. The igniter is a pronged strip of black metal in a housing wired with two plugs connected to power sockets underneath the Thermador cooktop.
Disconnect the two wired plugs on the end of the igniter from the sockets.
Take out the two screws in the metal plate that hold the igniter in position under the Thermador cooktop. Pull the igniter out of the mounting bracket in the cooktop.
Hold the new igniter by the housing and insert the part into the mounting bracket. Secure it with the two screws.
Connect the two wired plugs to the sockets. One plug is larger than the other, which makes it simple to connect them correctly.
Lower the Thermador cooktop into position on the countertop and reattach it with the screws through the underside of the front edge.
Plug in the cooktop's power cord and open the valve in the gas line.